That's why you are right, squad depth is very relevant, but sometimes it is nothing that the teams themselves can do a lot about. They either have those strikers available because they have a golden generation or they don't.
True. I think that's why some countries are trying their best to nationalize players or improve their grassroots competitions. At the end of the day, if you have a good infrastructure to produce good players, you'll eventually have a good amount of players to compete against other teams. It's the governing body's job to make sure they have a "golden generation" every few years or so (for developed countries at least). I don't think they can blame their luck if they don't even spend a single dime to improve it. CMIW.