Okay, let me clarify/amend: keep condos and other cases of split ownership of a single building as they are now, but do what I said for single-family homes and other cases where every structure is wholly owned by a single person.
A large amount of HOAs are on land leases, so they ARE shared ownership.
If you made the rule you suggest, all it would change is that new HOAs would all be on long term land leases (and you'd have a lot of chaos in the current ones that didn't do this because with existing laws it was not necessary).
Seems like it would be better to have a pool (or other common amenities) via voluntary contributions, leaving out the rules forced on homeowners' properties.
And a voluntarily financed pool makes a certain amount of sense. Why should someone who doesn't want to be involved be forced to contribute against their will? That's not easy to justify.