Not necessarily.
To look just at KLM, they are operating fewer frequencies than originally planned for the winter, and fewer frequencies than prior to the pandemic, on quite a few routes. As such, there is still scope to open new routes using these unused slots even as the overall number of slots at Schiphol is gradually reduced.
EDIT: Easyjet today announced that they will bring back the route to Southend; this hasn't been flown since at least 2020 (Easyjet stopped all operations at SEN due to the pandemic)
https://www.echo-news.co.uk/news/232...dam-announced/