A lot of developers struggle with Git. The only reason I don’t is because I’m interested in version control (too much according to some people I argue with).
Well I say that I don’t struggle but I’ve never had to use submodules.[1]
[1] Torvalds: people say that submodules is hard to use. True. But it’s gotten better now/it’s getting better. (Google Tech Talk 2007)
For me it comes down to how often something is holding you back. It’s perfectly reasonable for someone to only use the core Git operations, but if they’re losing work or having trouble collaborating that’s when I start to expect them to recognize that and try to improve.