Unfortunately, it is very hard to get the top tier players (irrespective of age) on the transfer market but it's not a major issue in my opinion and one can still rebuild.
It's always been difficult to get the top tier players especially the wonder young players but now the probability of you getting one has substantially decreased due to higher demand.
You can still buy average players for 500-900 but it will just take you longer to train and make your team stronger overall but you will get there at the end
Most important thing is to try make a long term plan so that you have strong players that will cover your expired players.