I experianced this myself and was pretty sure this is on purpose. If you request desktop on Chrome for Android you get a stretched out version of the mobile site and the auto complete of your keyboard makes the textbox on messages impossible to use. I think they want to funnel people to the app I just don't go on the site anymore.
Known issue and I'm yet to see a fix (other than "mbasic" which you have to use for messenger anyway).
Almost everything else seems to be fixed with uBlock Origin and/or Reading Mode.