With each new version of Android it seems Google takes away previously useful features and makes others harder to use. USB Mass Storage is one that went away a long time ago. Sadly there is no way to bring it back. Some more detail is at https://www.howtogeek.com/192732/android-usb-connections-explained-mtp-ptp-and-usb-mass-storage/
Some ideas are mentioned at https://android.stackexchange.com/questions/91900/is-there-a-viable-alternative-to-mtp-for-file-transfer but I'm not convinced they are any easier than just using ADB, especially since you still need the same USB drivers to do some of those ways too.
If you add an SD card, it can be inserted/removed and connected to a laptop or desktop that has a suitable adapter to read it. Just make sure it is not set up as "adopted storage" or it will be encrytped so Windows would not be able to read it. (Modern Linuxes can work with this once you extract the encryption key from your phone but it is something of a hassle to do.) But moving the SD card around all the time is something of a hassle, and you probably want to use MTP and/or ADB depending on the content to be moved.
In particular, the MTP protocol can only handle media. Meaning pictures, videos, soundclips, songs, etc. It will NOT want to let you move other content like PDFs, APKs, browser bookmarks, encryption keys, etc. It may sometimes be possible to rename something to be one of the allowed file types, transfer it with MTP, then use a file manager on your phone to rename it back, but that gets cumbersome after a while and in some locations may not even be allowed. So these other types of content are best handled with ADB.
Depends on your definition of "bloated", and of course assuming you are moving only suitable file types. You will need to install some device drivers (typically under 25MB). Probably best to get these from Xiaomi if possible, or there are some generics that can be used even with Windows XP. Oh, and you might need the Kernel-Mode Driver Framework (KB2685811 ?) if you don't already have it.
If you want to use ADB you will need to add the platform tools package (the latest version 34.0.5 still runs on W7, possibly even Vista, and is 12.2MB unpacked). Just unzip it somewhere, open a CMD window, make sure the unzipped folder is in that window's PATH variable, and you should be good to go. In case you have not used this before, there is a bit of explanation at https://developer.android.com/tools/adb and a command reference at https://adbshell.com/