Here's what I find.
If I can't find a tool, it's like I don't own it.
In fact, it's worse than that. If I know I own it, or even suspect that I might have one, then I will spend way too much time looking for it. So better to not even have it at all, and have to go get one at the store.
This is especially bad with misc. wrenches and sockets. A pile of them is worse than nothing, because you have to sort through every one, to find what you need.
So sets are important because they are organized. Even though they contain many sizes I will never use.
The next thing, is to get enough variety. You also need multiples of some things that are used together, like wrenches. And you need different lengths and sizes and types. Here again, you will buy some sets that you will use very infrequently. I find I need a balance, so I don't have to go shopping every time I want to do some task or job.
At some point you have the basics, and start getting specialty tools and tools that make the work easier.
But organization is still key. Tools need to be at the most efficient location for use and organized for identification. So you may need more than one set, if you use tools in more than one place.
This also means that unneeded tools should be eliminated or removed. They just complicate and confuse things, and make it harder to find what you need.
All this is from a homeowner perspective.
Bill