Each RV brand, and even models within brands will have different shower heads, so the performance will be different across the board.
So, it's a good idea to expect that yes, the shower pressure will suck and test the shower head and/or just replace it with a known good brand and type.
I would say buy an Oxygenics RV shower head. They're worth it. Just make sure that when you winterize (if you do) you take the head off the hose. Don't ask me how I learned that. hehe.
Sometimes it's not the RV its the pressure coming in, which can be mitigated by always using your on board pump and using the fresh tank.
It can also be the "usually" cheap shower heads they put in these things. (some brands have gone to putting quite fancy shower heads in, so I can't speak to those, and never bothered to test the one in our Valor).