If all you have is a hammer
I’m not sure about the saying, “If all you have is a hammer, everything looks like a nail”.
Even if you only have a hammer you still recognise the difference between a nail, a screw and a bolt. You know you can use your hammer pretty effectively on nails. You know using it on screws is going to be messy but might kind of work. And you know your hammer definitely isn’t going to work on bolts.
So, only having a hammer limits the problems you choose to tackle, it doesn’t mean you tackle them all in the same way.
Maybe the saying should be, “If all you have is a hammer, go find the nails that need knocking in”.