I understand the sentiment—and I'm of course biased (full disclosure: I'm the author of the PBEM mod for Command)—but it's worth trying it out if you haven't yet. It is somewhat different from the base game in that when you play Command with the PBEM mod, you are not giving orders in real-time—you give orders in distinct phases, and watch your units play them out simultaneously, WEGO-style. It makes the game more about delegation, planning, and command delay as opposed to real-time micromanagement. (Somewhat comparable to a PvP game in the Combat Mission series, if you're familiar.)
I've been working on this framework for almost a year to make sure that it's stable, reasonably easy to use, and fun to play, and it's been great to see the community picking it up and running games with it.
The CMO team is of course planning their own official RT multiplayer, as far as I know, but this PBEM mod will likely remain a different experience from what they have in development.
(But thank you for the link to active Harpoon 5 groups—would love to dip my toe into that at some point as well, time permitting.)