Microsoft 365, still unusable

The M1 hoopla prompted me to dig out my ancient MBA, update to the latest Catalina version and update Microsoft 365 to give it another spin. Here's what I ran into using Word:
1) Long documents still completely choke Voiceover. By long, I mean book-length. Navigating to the next page hangs for more than a second, and other tasks can just hang the machine indefinitely. Others have reported the same thing on here.
2) When opening the "customize keyboard" dialog, the focus doesn't move to the Window. I have to activate the window chooser to find the dialog.
3) Heading styles are navigable using the rotor, but heading styles are not reported in the text area.
4) the presence of comments are not reported in the text area. I am going to assume that other types of revisions like misspellings or track changes are likewise not reported. I didn't stick around to find out.
5) focus is still liable to jump back to the beginning if I edit a document without interacting with the text area, even though editing works just fine without interacting, so long as I don't switch to using a rotor action like moving by sentence. Pressing shift+f5 to go back to where I was previously editing works and moves the voiceover focus. "Voiceover follows keyboard focus" is selected in my settings, but doesn't appear to work as expected in Word.
Without access to Word on Mac, a Windows machine remains necessary for my work life, where things like Ulysses and Pages aren't adequate substitutes, though I use Ulysses for my personal and Web-oriented writing. And, so long as a Windows machine is necessary, everything else that works well/better under Mac OS works pretty much just as well on IOS with an external keyboard.
If others aren't encountering the above-listed issues using Word for Mac, then perhaps it's my mid-2013 MacBook Air to blame, so let me know if that's the case. Just being able to type a short document is not enough, though: usable means usable in a professional context, which means very long documents with heading styles, comments, track changes, etc. Usability in excel means announcement of column and header rows, which I've never gotten to work; and usability in PowerPoint means ability to edit slides effectively.