Older OS's were a lot more fun. XP had things like Clippy who helped you write essays and Rover who helped you find files:


You could also change them to a half dozen official Microsoft characters or install third party ones easily.
Today's search box is just a boring text box.
Windows also came with fun games like Space Pinball and Solitaire.
The games also had fun cheat codes like Pinball's mouse mode.
Microsoft also made productive software like Windows Movie Maker. Good luck trying to do something as simple as trim a video on Windows 11 without installing third party software.
A ton of software back then let you drastically change their appearances around:




Music programs used to show cool procederally generated videos synced to the music:
There were even official programs made by Microsoft that let you switch feature flags and enable features that were cool but not suitable for the whole market:

(I know PowerToys still exists, but today's version is just a collection of utility programs; they don't tweak the OS)
The shell was also extremely customizable and people shared tons of custom themes on DeviantArt and other sites.
There were also official Microsoft-made themes you could download:



and plently of third party ones ranging from terrible:

to quite well designed:



You could even make Windows look like Mac OS back in the day:
XP also let you embed web pages into your desktop background with Active Desktop:

and third-party widget software like Yahoo Widgets

and Rainmeter:

were popular.
Browser extensions (especially in Firefox) were incredibly powerful and could completely change the entire UI of the browser and do many powerful things that Chrome's gimped extensions can only dream of.
Fancy custom official and third party cursors were also a popular thing:





Websites would often load their own cursors just to be cool.
Today, I don't know anyone who even knows that Windows cursors can be changed with an ".cur" or ".ani" file.
The OS Icons could also be changed similarly to how cursors were changed and a lot of people downloaded cool themed icon sets.
The older Windows also made a lot of cool sound effects, which you could also customize.
Security was also terrible back then and it was possible through simple scripts and hidden button clicks to bypass school admin lockouts. If a kid wanted to play games on school computers, they had to learn stuff like that. Today, they just pull out a phone and swear at the teacher if they get asked to put it away.
This is just scratching the tip of the iceberg of the type of stuff a kid could do back in the day.
Kids can't really do any of this stuff anymore. While it is still possible to theme Windows 11; it's no longer part of popular culture to do so and there is no way that a kid would know about software from "boomer" companies like Stardock that let you customize Windows unless their technically inclined father explicitly told them about it.
Where is the fun in today's computers?