To try to tackle this, the Welsh Labour government, alongside Plaid Cymru, introduced measures to curb second-home ownership. This included giving councils the ability to push council tax on second homes to 300% the usual rate. They also closed a loophole whereby second-home owners could register as a business in order to pay the much lower business rates.
Gwynedd council used these powers to hike council tax to 150% in April 2023. By the end of 2024, house prices had fallen by 12.4% as second-home owners tried to sell up. In Pembrokeshire, house prices fell by 8.9% after the council increased the council tax to 200% on second homes (though this was reduced to 150% recently).
Just my experience having had a cottage far away from everything with other cottages around, the few of them available for short term rental were either unavailable most of the time as the owners didn’t want to have to travel hours just to clean up every weekend and those that were available at all times were owned by people who also lived around there full time.