A few notes:

Windows 11 is Windows 10 with exactly two changes; Windows 10 is not Windows 8 with several changes, but still in the same branch/evolution in the same NT family.

The first change is: the Sun Valley theme update, which finally gives all the WinForms/WPF/UWP/WinUI apps ("Metro" or "Modern" style) apps a real theme instead of bad full-white and full-black themes that destroy any sense of visual ergonomics Windows had. Microsoft was afraid people would be confused and need to be retrained in corporate environments (fun fact: this happened when Vista became 7), so they increased the major version.

The second change is: VBS (Virtualization Based Security) is now enabled by default and the installer won't let you install without it working. This means UEFI must be enabled, legacy boot must be disabled, secureboot via TPM must be enabled, and due to the previous one, your TPM must be enabled and new enough, else you cannot use Windows 11 (unless you do an underdocumented hack to the installer; I did this on my Ivy Bridge laptop, I know what I'm doing and I accept the risk). All Skylake family CPUs and all Zen family CPUs have a firwmare TPM that meets requirements; first generation Skylake and Zen 1 have security vulnerabilities that blacklist them from default Windows 11 installations (or, roughly, to run Windows 11, you need a CPU made in the past ~5 years). Again, because hardware requirements changed (even though "sold with Windows 10" required such features exist in the first place), major version changed.

The second change is not a huge issue either, as all sold-with/for-Windows-10 machines are required to have these features; the flaw is, many mobos default to being broke out of the box, as in, TPM is not enabled, secureboot isn't turned on, and hypervisor CPU features are not enabled: these are technically defective mobos whose fix is to just turn the features on. Some mobos have gotten Windows 11 BIOS updates that just change their defaults and turn it on; 99.9% of users have no clue what I just wrote or what any of it means... and a BIOS update won't fix this because they, again, have no clue what any of this means.

Now, one last thing, the semi-kicker: with the first change, they finally jettisoned the old taskbar: it predates the original Metro UI, and is very finnicky to work with as it has a lot of custom behavior. The new one is written entirely in normal XAML as a completely normal and conventional app.

Why is this a semi-kicker? If you use small taskbar and/or task grouping disabled, as you're a competent and knowledgeable Windows user, you need to use Explorer Patcher to re-enable both of those features. Microsoft is currently denying the lack of those features are a bug, and do not understand that their decision has already been vetoed by the community and some of their largest enterprise customers.

Their reasoning is that both Apple and Google poison kids in education environments by putting Macs and Chromebooks in school and making that their first exposure to computing, so instead of fighting this, they default to an identically functioning dock-esque giant centered task-grouping taskbar instead of, you know, the one you expect from a product named Windows.

So yeah, go accept the upgrade, then install Explorer Patcher to fix the backwards taskbar issues.