I live off of a MUP like you describe. Older, curvy, lots of kids, lots of advanced age folks walking hand in hand, etc... I've seen it, and also those pesky one-wheeled thingamabob electric things.
I feel everybody could abuse the trail rules as a user, no matter the vehicle. So try not to judge on that alone.
I think all we can do is participate in our municipalities. Make friends with folks involved in local cycling with connections to representatives. Then voice a concern a new challenge has arisen that needs attention. Nothing nasty, just a new challenge to figure out. Maybe a small use study in-person to observe trail user types. Then update the rules and infrastructure of trails seeing the traffic changes.