Bandwidth never was the problem with MIDI, that is actually enough, but your right with _some_ devices in the 80s/90s, that the processor was under-powered for the bandwidth. For example my Roland Alpha Juno 2 from 1986 is somewhat under-powered and not the tightest, but my Casio CZ-5000 also from 1986 is just doing fine! I mean this is almost 40 years ago and there were device that could handle it without problems. The problem with USB though is, that is does buffer in a "non real time safe" way, which leads to unpredictable jitter and interrupts. That means, for MIDI, USB is worse then the original DIN connection.

I am not talking of MIDI in a DAW, without any physical connections, this works just fine.