I find usually the thing you described in this hobby as being something suspect which ends up not being the solution but would have caused major trouble down the line anyways - being wrong basically, but saving yourself work in the future on something you had no clue was wrong in the first place and sometimes chalking it up to "also contributed". That being said, there are a lot of things in this hobby that would genuinely do what you say. Especially on flippers - the parts are shot but some idiot also oiled everything and made it even worse. You can fix either and it would get a little better, but in order to really make it perfect you HAVE to fix both.

And other times, it's just impossible to know. I usually just say "Well if it didn't fix it, it definitely needed it anyways" (especially when getting paid and using process of elimination but also trying not to look like you've got it wrong), and it's very true in this and the arcade hobby.

I service arcade monitors and if you're pulling it apart and haven't done it you basically should always replace ALL of the old capacitors while it's out which is basically used as a "baseline". It's useless to try and fix a problem without that steady base, and it ends up fixing 80% of the problems you can find completely anyways right away. And even if it didn't fix the problem, it likely fixed contributing factors to it that could have made it worse, or at least, they would have become a major problem shortly anyways so it definitely needed it.

Very many "options" in this hobby for what a problem could be, many with multiple answers that all need to be addressed and fixed for a very proper and long-lasting solution.