Opening hours of these pools are usually terrible. Many of them are closed on Sunday. Most of them are closed in the summer. If you are working 9-5 during the week you will have a hard time finding a pool close by where you can actually go swimming. E.g. in the article they write Berlin has 60 indoor pools. But at the moment only 28 are open: https://www.berlinerbaeder.de/aktuelles/detail/geoeffnete-ha...

And don't go there with family and small kids. Changing rooms are much too small for families. And most of these old indoor pools have no kids area to speak of. These pools are just good for nice photos on Instagram or some blogs about architecture of the past.