I would strongly disagree that we're losing players to rugby. While rugby is (IMO[0]) the second sport in Scotland far more youngsters play football than rugby, and in practical terms the potential for making a career out of rugby is more unlikely than football. So I don't think that we're spreading ourselves more thinly than Croatia are, I think there's something more to it than that.

[0] - I actually read a while back that Cricket had more registered players than Rugby in Scotland, but I take this with a pinch of salt. But make no doubt about it, our sporting focus is roughly similarly focussed on Football to Croatia's.