It wouldn't surprise me if you're experiencing that old bug that happened when iOS users went to android. Their phone number would be in apples system as an iMessage number, and wouldn't recognize that it wasn't. So people would message you, and the message would get lost in the aether.
I don't understand what beeper is doing (cause I'm dumb and too lazy to look it up) but your number might be stuck. Your friends might need to manually turn off iMessage for you (it used to be long pressing the send button in the message till it turns green)
I reallt hope apple actually adopts RCS next year. The standard is so much better than iMessage.
Technically apple users can fix the quality issue with a change in their settings to stop compression of images sent via MMS.
As to android phones not having high quality, your def right about that. The RCS rollout was terrible. But most of the flagship devices have RCS and a lot more carriers are allowing it (here in Canada at least. I assume we're behind the curve though)
Samsung has enabled RCS down to even their cheapest handsets, (I believe) but apple isn't adopting that till next year, and then we'll be able to skip the shenanigans