We will still watch Croatia's matches with the best line-up to date, with Modric and co, until Euro 2024, then only time will tell if it was only 3 or 4 players who were making all the difference, or if the country's soccer has really evolved and they will be able to continue with good results in the near future.
I can't give a clear opinion because Modric was an excellent reference for this team, even more with the Real Madrid / Champions League experience he had.


Only talking about Euro 2024 and the qualifiers:
I believe Belgium will get that qualification, because their group is not strong enough to consider a real treat
In my opinion Estonia and Azerbaijan will not make it, while Sweden and Austria will fight for second place, and Belgium will qualify first.

I think they will can be a great team for Euro 2024 and be competitive, but it is a good time to reformulate the team already thinking about the 2024 Euro and 2026 World Cup. I would be disappointed if they kept exactly the same players that played in the last World Cup and ruined a whole job because of internal fights.
Another reason to believe in a good Belgian campaign is that the other teams are not that good either.
I can only see France (ok, maybe England too) with an extremely strong and consistent team with the right mix of new and experienced players, who already have the foundation laid for several years.
The rest are all at the end of their cycle or trying to get a new team right.