Even before all of the articles and complaints about the now required Facebook Messenger app, I'd already decided that I was NOT going to add it to my phone. I still haven't installed the latest update of the Facebook app, so I certainly wasn't going to add another, separate Facebook Messenger app to my phone.
I use Facebook just as much as the next person, but I'm mostly a computer Facebook user. I check the Facebook app on my phone occasionally, and I certainly don't use the messenger often enough on my phone that I need to add another app. It's not worth it.
I've ignored the "install the Messenger app" suggestions for months, but the other day I was banned from accessing a message on my phone. It ticked me off (like many others), but then I wondered: "if I open Facebook on the phone's browser, can I access my messages?"
Answer: Yes, you can! I opened my messages and replied from Facebook within the browser the same as I'd always done in the Facebook app. Easy and effective... until Facebook bans the messenger on the mobile device browsers too, which I doubt they can or will do. But who knows?!
So, the solution: instead of downloading the Facebook Messenger App, taking up more space on your phones storage, cringing over the privacy concerns, and cursing Facebook for requiring users to have two apps instead of one (and where will that end?), just use your mobile device's browser to access your messages. See, there is a solution despite some websites suggesting we all just have to do as Facebook
Yes, you'll still have to access two different apps on your device just to see Facebook and to check messages in another app (the browser), but you were going to have to use two apps anyway. At least with this workaround, you won't have to download another app (no matter how small the file size is) since all mobile devices come with browsers--sometimes two.
Alternatively, you could completely unplug from Facebook, delete your account, and find other social media OR go play outside.