I'm wondering because my wife has a subscription to speechify (commercial text to speech app), and uses it to listen to online textbooks. It has recently pretty much stopped working properly (auto-reads headers, but not the main text of the book). I thought it might be due to MV3 and the extension no longer being able to parse the page properly.
I was about to try the chrome variants that haven't gone to MV2, but I guess this removal of MV2 exensions would mean that all MV2 browsers are now crippled..