The YouTube and social media eras made everyone so damn dramatic. :/
Mosh solves a problem. tmux provides a "solution" for some that resolves a design decision that can impact some user workflows.
I guess what I'm saying here, is it you NEED mosh, then running tmux is not even a hard ask.
1. High latency, maybe even packet-dropping connections;
2. You’re roaming and don’t want to get disconnected all the time.
For 2, sure tmux is mostly okay, it’s not as versatile as the native buffer if you use a good terminal emulator but whatever. For 1, using tmux in mosh gives you an awful, high latency scrollback buffer compared to the local one you get with regular ssh. And you were specifically taking about 1.
For read-heavy, reconnectable workloads over high latency connections I definitely choose ssh over mosh or mosh+tmux and live with the keystroke latency. So saying it’s a huge downside is not an exaggeration at all.
From my stance, and where I've used mosh has been in performing quick actions on routers and servers that may have bad connections to them, or may be under DDoS, etc. "Read" is extremely limited.
So from that perspective and use case, the "huge downside" has never been a problem.
Not a scroll back buffer workflow issue.