Think it's just a classic multiple things can be true at once situation:
We were massively punching above our weight in 2019 and 2020 - at that time, non-big 6 club finishing in the top 6 in the PL era was exceedingly rare. In one of those attempts at the top 4, Man Utd spent £65m on Bruno Fernandes in Jan to get them over the line and pip us. How can we compete with that?
Finishing 5th both times after being in the top 4 for so long was a crumble/bottle situation, perhaps indicative of the soft mentality/underbelly that developed in the latter half of Rodger's tenure
But finishing 5th twice was a huge achievement for the club based on an historical perspective for the club and for a non-big 6 club
Performance in subsequent 2nd/3rd tier European competitions was poor (even if we did eventually get knocked out by Mourinho's Roma)
'medium' sized clubs that have done well since is largely due to 1) the PL getting more competitive; 2) those kinds of teams have upskilled; 3) 2nd/3rd tier European competitions have gotten 'easier' due to format changes