That's why I mentioned rootless containers specifically. In those, root is at most the user running the container. It can't do a whole lot, because it's not really root. Each user in /etc/subuid gets a range of dummy IDs >65535 specifically for containers for that user. When outside the container, everything shows as owned by the user, so root in the container can't even result in root owned files on the host, so no suid trickery or anything.
Of course you should still run as a user in the container too, I was just pointing out in rootless containers the blast radius is much reduced because of that feature. Definitely still don't want root for many other reasons.