Besides Son, the players you mentioned play in a different position compared with Dybala. IMO we should compare Dybala with second strikers / false 9s like Griezmann, Felix, Firminho, etc.
But you are right, he can't beat a man at pace. That's one of his limitations, we need to focus on his strengths. For that reason, he is better in the center than playing wide as a winger.
For his position, I'm happy enough with him especially if it's a trade for Lukaku given how he stunk up the place last year. But we need a RW - we have enough options for the striker role currently and we don't really play with a no.10, the trend has been largely to play with a front 3 nowadays. RW is an area of the field we've neglected, and it makes our attack easy to suss out because oppositions can pretty much forget about needing to defend that right hand side.
I'd disagree that Dybala isn't fast, faster than Bernardo, and that all wingers must be lightning quick - see (young) Ribery, Draxler, Mahrez.
But even if your criticisms were correct, couldn't Dybala then play an Eriksen-type role?
In any case Dybala naturally drifts out to the right no matter his starting position so if combined with Wan-Bissaka's incredible overlapping pace that would solve your right wing problem would it not?
Your are correct - Bernado for instance I didn't think was that great, but the lad can dribble and is very technical. He's helped by Pep's system but he's hard working and would be a great player for any team on the RW. Ditto Ribery. Mahrez I would count as pacey, and Draxler I would count alongside the James Rodriques, Iscos etc's of the world - good with the ball at their feet but struggle to start for their teams because of similar limitations - they struggle to beat a man consistently / lack pace / don't make runs in behind.
Now Dybala could turn out to be the like Bernado / Ribery - I haven't watched him much outside of CL matches - but from what I've seen the fact that he can't beat a man will have him be similar to Mata / Lingard already - good work rate, good / decent technique, but when they get the ball they slow things down or have to pass the ball sideways / backwards.
Most of the top teams now have at least one wide forward that can consistently beat a man with pace, it keeps defenders pegged back. We pretty much have none considering Martial is inconsistent / might play as a CF this year.