Notably, I have already "learned something new" as I have been using Windows 10 for quite some time already, so on that note you may feel free to shove your condescending manner where the sun doesn't shine. The onus is on you to prove that your beloved new shiny interface is better than the one it replaced because you made the original claim of superiority. You have refused to back that claim with specific points, so we can safely assume you don't have any points to raise in favor of your position. However, my position is easily defended, so I will gladly do so now...not for you, but for other readers that are actually interested in a discussion on this subject.
Windows 7's Start menu consists of two columns. The left column contains frequently used and user-pinned programs, with optional sub-menus to open recent documents and perform common tasks associated with that program. Windows 10 has replaced this with pinned tiles and a "frequently used" section at the top of the full program list. The sub-menus for common tasks and recent documents are completely gone.
Recent documents are now accessed via File Explorer and the view of these files cannot be grouped by associated program at all.
Pinned tiles take up a large amount of screen space and are the most distant items from the Start button, increasing the amount of movement needed to reach the desired application. This is worse on low-resolution screens since less pinned tiles can be shown and the user may have to scroll in addition to moving the mouse over more distance. While the tile target size is somewhat larger than a pinned Start program in "large icons" display mode, the extra distance and two-dimensional layout cancels out the benefits of the larger target due to requiring a longer (and therefore less accurate) motion to reach.
Pinned and frequently used programs on Windows 7's Start menu can be changed from to "use small icons," increasing the density of what can be pinned there without reducing target size horizontally. Pinned tiles reduced to the equivalent size are reduced in both dimensions and lose their text labels completely, reducing target size to 1/4 (requiring more focus from the user to accurately hit) and forcing reliance on the icon alone to quickly select the desired application. Icons are hard to get right and only enhance usability under specific conditions
and "A user’s understanding of an icon is based on previous experience. Due to the absence of a standard usage for most icons, text labels are necessary to communicate the meaning and reduce ambiguity."
Hovering over the tile will reveal the label via a tooltip, but this is not sufficient as each tile would have to be hovered over by the user to read all of them whereas displaying text labels for everything enables the user to scan quickly for the name they're interested in.
Windows 7's Start menu has a customizable right-hand column which comes with these (mostly sensible) defaults: User's home folder, Documents, Pictures, Music, Games, Computer, Control Panel, Devices and Printers, Default Programs. The lack of the Downloads shortcut by default is problematic, but the ability to add it exists in an intuitive location. The utility of some options is highly debatable but since they're fully customizable the user can choose new defaults that are more sensible to them. Regardless of what programs (the left column) a user might want to use, all but the most novice users will inevitably need to reach their home folders, the Control Panel, and internal, optical, and external storage media under Computer (aka This PC on Win8+) on a regular basis. Windows 10's Start menu does not provide any of these as first-level shortcuts. Windows 10 provides by default a user icon, File Explorer, Settings, and Power, with the user's icon only doing some functions that Power used to do (sign out/log off) and allowing quicker access to the user account settings in the Settings panel. It is possible to add some of the Windows 7 functionality to the skinny left-most portion of the Start menu but they do not have text labels, represented only by flat abstract icons; in addition to finding where to customize and add these items back, the user must learn what the icons are to use them, increasing the learning curve for the system (though this isn't as big of an issue once they can recognize the icons.) In the Anniversary Update, Microsoft removed the ability to arrow-key navigate these leftmost icons, so power users can no longer press e.g. WIN, UP, UP, UP, ENTER to open File Explorer without the use of a pointing device, nor can they press WIN, UP, ENTER to access the power menu and quickly shut down or restart.
Notably, the Windows 7-style Control Panel that can be reached via Start still exists in Windows 10 and is required to access a plethora of settings that the Windows 10 Settings panel lacks, yet it is completely unavailable in the Windows 10 Start menu. The only paths to the classic Control Panel are through Settings panels that have links which open a relevant classic control panel, via a shortcut the user must place somewhere themselves (meaning only experienced users who already know that making a new shortcut to 'control' or capable of finding the now-hidden Desktop Icons control panel and activating the hidden Control Panel desktop icon), or through the hidden right-click-on-Start menu.
Speaking of the Start button right-click menu, this illustrates a severe problem with Windows 10 relative to Windows 7: a lack of discoverability.
The only way to know that this menu exists is to either be told by someone else that you can right-click the Start button to get it or to accidentally right-click the Start button and discover it that way. There is no indication or tutorial tip that tells the user that they can right-click the Start button to get a spiffy administrative menu. There is nothing that tells the user that WIN + X brings up this menu. The user has to learn from someone else about it or make a happy mistake to discover the feature. Windows 7 doesn't have such tutorials either, but it also doesn't have a fancy right-click menu that bypasses most of the brain-dead Windows 10 schizophrenia for power users in the first place.
Hovering over Computer, Documents, All Programs, etc. on Windows 7's Start menu will show tooltips explaining what they will do if you click on them. Windows 10 will only display the missing text label, so instead of "Find Internet downloads and links to favorite websites" as the tooltip for the Downloads folder icon, you'll only see "Downloads." For experienced users this isn't a problem; for novice users it might be...but then again, they'd have to figure out how to get Downloads to appear there long before they could read the help text it displays.
In Windows 7, a user can right-click on the taskbar or Start button or an empty part of the Start menu, click Properties, and access the Start menu customization settings (or go to Start, Control Panel, Taskbar and Start Menu); clicking Customize then shows all of the right-hand menu items and behavior-changing options available. In Windows 10, the basic customization has been moved to Start, Settings, Personalization, Start. All behavior modification settings except for "recent programs/apps" and "recent files" are gone. The "Customize" button is now a "choose which folders appear..." link that (just like ALL of the "links" in Windows 10 Settings panels) has no hints that it is a clickable item. Control Panel, Devices and Printers, and the Run... box are not available to add to the left-hand side.
I could go on, and this whole thing is entirely about JUST THE START MENU in Windows 10 vs. Windows 7. This is ignoring every other regression that Windows 10 introduced and focusing on only one aspect of the system.
I'm waiting on your equally well-thought-out response.