I'd try to use the phone for a bit as it is (after updates and a reset) to get an idea of what Xiaomi's Android is. Their "ROM" is a bit different from Samsung's, Samsung's is different from what you'll find on a Google Pixel, etc. The level of bloat is also different, which cheap Xiaomi devices coming with more crap than their more expensive devices.
Then I'd try a custom ROM like LineageOS to see if it's better for my use than the stock Xiaomi ROM. There are trade-offs. For example, you won't be able make contactless payments out of the box. If you decide not to use Google Apps, you won't have an app store, many banking apps won't work, you'll break notifications on some apps, etc. LineageOS, while stable, doesn't have a paid team testing every setting of the phone to see if it works.
If you like this custom ROM thing, there are other less "professional" custom ROMs in places like XDA developers with more features. Just keep in mind that they probably won't be as stable as Lineage or the original Xiaomi ROM.
If you prefer to use the stock ROM, but want to remove the bloat, there are tools like this one:
https://github.com/0x192/universal-android-debloater
You can "jump" right away, but then you might get the wrong idea about Android. Your opinion about iPhones wouldn't be the same if the first time you used one you tried to jailbreak it, remove all Apple services, etc. Or if you moved to Linux and started tweaking and compiling the kernel yourself instead of just installing Ubuntu. It won't be a smooth experience and there's a lot to learn.
I'm fine with custom ROMs. I've been using LineageOS (or CyanogenMod as it was called back then) for the most of the past 7 years. I'm okay with the trade-offs and can fix almost every issue that arises from time to time, but this is not something my parents or most of my friends would want to use. I like to thinker with my devices while they just want them to work.