Sorry for taking ages to reply, got caught up in something and boom then it was time to go to bed
Anyways, It is possible to do some fair numbers, and our opening burst on ST bosses can be pretty sick. But if you did raid during Legion, take the frustration you remember feeling about our mobility during Legion raids (it was annoying alright, but you could live with it) and then amplify it about 5 times. Our movement is what it is, can't do much about it, but it sure is annoying and I've had times when the frustration made me almost want to stab someone :x
Then when it comes to our cleave and aoe we could do well in Legion, to a point where we felt useful and even strong on some fights - in BfA this is much harder to achieve, especially since we seem to scale poorly with gear so the more gear everyone gets it only broadens the gap between Rets and other DPS specs. So something is up, and I personally also misses how Rets felt to play in Legion when we had our Legendaries, our Tier sets, trinkets, the artifact weapon and its traits and NO GCD's ruining the flow :'( BfA Retribution feels like an outright downgrade in comparison to Legion Retribution.
I'm currently choosing between DH and Rogue atm, but haven't decided yet. It saddens my Paladin heart, but it is what it is. I too am sure OP will find a suiting melee class to play, it's just a shame that Ret paladin prob won't be it.