Is there any IaC solutions where you can “simply switch between cloud providers”?

This isn’t a limitation of TF, it’s an intended consequence of cloud vendor lock in

I believe the usual uninformed thinking is "terraform exists outside of AWS, so I can move off of AWS" versus "we have used CF or Bicep, now we're stuck" kind of deal

Which is to say both of you are correct, but OP was highlighting the improper expectations of "if we write in TF, sure it sucks balls but we can then just pivot to $other_cloud" not realizing it's untrue and now you've used a rusty paintbrush as a screwdriver