Some facilities should be free because they're intended to be fully accessible by everyone in a community, which means if the demand outstrips the capacity, the capacity should be raised. If the library or gym or cafeteria is too full, there needs to be a new one built. The exceptions would be unique or high-demand spaces that couldn't feasibly be accessible by everyone all the time, in which case you would have to ration them in some manner or another. But even then they wouldn't necessarily need to have a cost, per se. Provincial parks in Canada, as an example, offer very cheap camping, but you have to book in advance during times of high demand. They are essentially free, something like $6/night per campsite, with the fee mostly being a good faith payment to ensure that you're not just squatting on the reservations. Other than the very modest fee, the rationing is done via people making plans ahead of time for use of the parks, which is a reasonable enough way to handle it.
One thing about communal spaces under socialism is that there should be way more spaces available to everyone. Without the incentive to make places exclusive for profit, there should be a lot more capacity overall to accommodate communal areas. The question is more about what kinds of services are required for communal spaces, because that's where the real cost comes in. Buildings require maintenance, swimming pools require lifeguards, bars require bartenders, etc. and that's where there might be fees required or useful to ensure that it's worthwhile to maintain the programming within those spaces.
Some facilities should be free because they're intended to be fully accessible by everyone in a community, which means if the demand outstrips the capacity, the capacity should be raised. If the library or gym or cafeteria is too full, there needs to be a new one built. The exceptions would be unique or high-demand spaces that couldn't feasibly be accessible by everyone all the time, in which case you would have to ration them in some manner or another. But even then they wouldn't necessarily need to have a cost, per se. Provincial parks in Canada, as an example, offer very cheap camping, but you have to book in advance during times of high demand. They are essentially free, something like $6/night per campsite, with the fee mostly being a good faith payment to ensure that you're not just squatting on the reservations. Other than the very modest fee, the rationing is done via people making plans ahead of time for use of the parks, which is a reasonable enough way to handle it.
One thing about communal spaces under socialism is that there should be way more spaces available to everyone. Without the incentive to make places exclusive for profit, there should be a lot more capacity overall to accommodate communal areas. The question is more about what kinds of services are required for communal spaces, because that's where the real cost comes in. Buildings require maintenance, swimming pools require lifeguards, bars require bartenders, etc. and that's where there might be fees required or useful to ensure that it's worthwhile to maintain the programming within those spaces.