I suggest that we discuss the claim that the Croatian national team is old on the basis of concrete arguments and facts, not opinions. Let's take a look at all the main players of the Croatian national team who are expected to play in the Nations League and EURO qualifiers and check their age.
If you look at my posts here, you will see that I am an admirer of the Croatia team, and I think most people underestimate the team to this day.
What I think happens with most people who quote the age of the Croatian team, might be the fact that they have Modric as their main player, and consider that the Modric era is coming to an end.
Just like every team has someone who draws more attention, like Mbapeé, Neymar, Harry Kane etc, Croatia had / has, Modric.
Obviously they have other excellent players, and you don't get to the results they had with just 1 player.
Perisic is also another player with 34 years old, Brozovic and Kovacic with 28 are in the middle ground, neither too old, nor too young hehehe.
I believe when they talk about Croatia, they talk about it, but I don't agree with what they talk about, that Croatia is on downtrend.