This is an interesting issue, with multiple fronts:

• Spain has a large chunk of its GDP tied to tourism, but...
• Some places are getting overcrowded, like Ibiza, Barcelona, or Madrid, which discourages tourism.
• Having a large number or holiday apartments, increases housing prices for local residents...
• And causes noise issues during the holiday season...
• And makes it difficult for seasonal workers to find a place to live.
• While during the off-season, it leaves a lot of apartments unoccupied, making them an easy target for illegal occupation, with whole gangs living from it, which then require LEO resources to vacate them...
• And makes it extra difficult for local non-tourism businesses to survive...
• To the point that they're converting business locals into... holiday apartments.

The plan to shut "all" holiday apartments is kind of a pipe dream, or part of populist politics... more so in Barcelona, where right now the recent elections have left Catalonia with parties so divided, that they can't even agree on a viable candidate to lead it.

A slightly more realistic issue to tackle, are "illegal" holiday apartments that don't pay the corresponding taxes. Some estimate that Madrid has a 10:1 ratio of illegal vs. registered holiday apartments.

But in general, there is currently no solution that would keep those apartments occupied all year round, without neighbor conflict, in areas that live mainly off seasonal tourism.

For example, Ibiza has 40K permanent residents, but capacity for 600K tourists, which leads to seasonal workers living in trailer parks, or even in their own cars.