The socialists want to power and control everything, so they would always accept new EU members, especially dependent ones.
The greater threat to the EU is if the UK thrives after Brexit and more nations look to leave....Brussels will take anyone to keep their power.
You can start at 31:30 if you’re interested in another view from across the pond:
https://ricochet.com/podcast/ricochet-podcast/boris-and-blightys-big-day/
He suggests Spain would veto their application because Spain doesn’t want to encourage their own Catalan.
He also notes how dependent Scotland is on UK subsidies for their economy.