As a user of both, I don't really see anything missing from OpenRC. Maybe parallel startup? Hasn't been a bottleneck for me, ever. I prefer the "syslog" way over journald but that's not anything like a deal breaker. What's features I'm missing?
Was looking into this exact thing this week. Amusingly, the suggestion I read on the gentoo wiki is to run a user instance of runit, which... I actually like that, but it does start to beg the question of why not use that everywhere.
I also make heavy use of user services, TPM encrypted secrets, systemd tmpfile directories, etc.
Another thing: systemd-networkd is the only Linux networking stack I've managed to get working reliably with tailscale's dns and a private dns service on my workstation.