That's a great idea, as long as the hard separation goes both ways with bikes no longer being allowed in car lanes.
Yes this means you can drive a scissor lift or mobility scooter in stop and go rush hour crap. Whatever, I guess that's fine.
There already exists roads where cyclists can't be: Highways/motorways. If the problem is cyclists in the road, that solves itself by building better infrastructure. Where there's adequate cycling infrastructure, cyclists prefer to use it. Where there's lacking or none, one should of course be able to use the road. Otherwise it would be a de facto ban on cycling, which I'm sure was your point?
It's from a combination of getting stuck behind cyclists going really slowly and with no opportunity to pass them, and from so much blatantly illegal behavior by them like running red lights without even slowing down.