Dunno what to tell you. Several possible points of failure there. Maybe your bank's system for sending SMS just sucks. Maybe you're in a place with poor mobile network coverage (which is a real problem for SMS 2FA, I agree, having lived in a place with nearly none for several years).
But for me, where I live now, with my bank, and my phone carrier, it works great. Never had a problem that I can think of. Typically, the SMS arrives within seconds. It's the least annoying and most reliable 2FA method I use.
I'm not that worried about potential security issues. Sure, it's a possible problem, but pretty low on the list of things to worry about.