Does more ammo types translate into better overall gameplay when you have to keep track of twice or trice the ammunition types and what weapons they cater to?
Personally, I don't think so. I don't like ammo types being overly limited either but when we have dozens of ammo types then as someone who isn't a gun nut it isn't exactly easy to keep track of what is what and what the difference between all of it is.
If there are too many weapons then that obfuscates the niche of weapons. What makes X different from Y and Z? In what situation would I use X over Z? I don't like having 40 SMG's that do the same thing.
Less isn't more, but less can be better than more.