If we trade down, it's to select more top shelf talent, even if it's not at the tippest of the tippy top there's usually hits all the way down the first round and a lot of those guys can help you win games. Trading down will be for the purpose of getting more picks and drafting more bodies. This has advantages.
In fact I'd venture to say that as shallow as our rosster is, we need, most of all, a broad infusion of talent rather than a couple peak guys. We need energetic young depth and we need help in a lot of different places, more than can easily be addressed by 1-2 guys.
There's very few teams that can actually use the quarterback to cover ALL their flaws. the Bengals and Chargers certainly tried, and their primo quarterbacks are getting murdered and now struggling with injuries only a few years later.
to say nothing of what happened to the Jets when they tried to cover their considerable roster issues with Aaron Rodgers.
Generally it's better to ACTUALLY ADDRESS YOUR ISSUES rather than trying to sweep them under the rug and distract everyone with a shiny new toy instead.
I'd rather get a second round talent at QB if it means that we also get the help we need in the trenches on both ends of the ball, and also help at linebacker which is a perennial need for every team ever.
If the goal is to make this year look better, then certainly a trade down to acquire more pieces is the play. But if you want to build a long term contender, you need that top shelf QB. Other than SF, every contender in the league has an MVP level QB. You can't compete against that with a Brock Purdy, unless the rest of your roster is nothing but pro bowlers and all pros. Even if we are optimistic about the Wolf regime, it is hard to fathom they are going to be SF level at drafting and developing. A great QB doesn't cover up all your issues, but it does cover up a lot of them, just look at what Mahomes did with KC and what Brady did when he was here.
The holes on the roster should've been filled with FA, but the FO decided to sit on their cans and not add anything there. It is a very risky strategy to build a roster via draft only, especially when u have the cap space to add some pieces in FA.