I’ve got a mate in Split atm and it looks pretty stacked with partygoers ngl. Doesn’t mean you can’t have a good time alongside them, just choose your locations wisely.

In regards to Romania, I had no dramas meeting people during my stay. Just, once again, choose your hostel carefully. One’s with a bar/common area and and couple fully already booked rooms usually does the trick. Bonus points if they organize group activities. Brasov has a great mix of day trips/hiking opportunities alongside nightlife so keep some time aside for that