I think Drew Lock has the ability to be a very capable starting NFL quarterback. He might have a ceiling, similar to how I think Geno seems to have a ceiling, but we need to see him in a full season.
I will say this, putting a great quarterback on this team right now wouldn't make them appreciably better. The playcalling and offensive line play is just too bad. So I don't think we should judge Geno or Drew too harshly. I do think they both have made poor decisions, which is infuriating, but I try to take into context that they are trying to overcome some bad play calls and a bad O-line.
You put Brock Purdy on the Seahawks and he is an unmitigated disaster. This is why I would hold off on drafting a QB unless John sees a bargain (like Russell). Too many top QB's flame out. I think Drew can play in this league, but let's see. I know some pundits on Seattle radio have just plain given up on him after a single fill-in game.
That seems absurd to me. San Fran has shown that if you build a great team you can plug in someone like Brock Purdy at QB and dominate.