That's the problem: Any task can indeed be screwed up. It can be worse than it was before.
A new, not-oversize cover plate that actually-matches in color is fine. As you suggest, it is trivial to get that right.
But people screw it up anyway, and when they do so it represents a distinct lack of attention to detail. If I find that along the presence of other new electrical stuff, like outlets with USB jacks, smart home dimmer switches, and can lights with fixed LED elements, then... man. They obviously couldn't even get the outlet covers right. What else did they screw up, that I can't see?
Old caulk that was skillfully applied and remains in good shape isn't a problem; it is not broken and does not need fixing. New caulk that is well-done isn't necessarily an issue at all. Both communicate that a base level of positive care for the quality of the home was present.
But when it's sloppy, it's a clear indicator that they just didn't care much at all during the process. There's direct evidence that they were unwilling to put the effort into making a smooth bead of caulk instead of a messy one. They didn't care about that part of this small job, and by extension they probably didn't care about what they were covering up (whether it was good, bad, or indifferent).
Anyway, maybe the lazy fixes work for enough buyers that it does increase the sale price, and that's good for a seller.
It doesn't work for me, though. The presence of these kinds of things brings me more questions than it does answers.
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The answer that maximizes the price by satisfying all potential buyers is to do careful and correct fixes. If the quick fix makes some money, then a good fix makes even more money. Take the time to get it right.