The overall ranking is based on a rolling five-year coefficient.
But I agree with your overall point in the whole point of revising the Champions League for next season and beyond was to get more “Big Five” teams in there to get more money, have more opportunities to win, get more points for themselves, and to keep themselves at the top. It’s a self-fulfilling prophecy at this point.
Next year, Italy might have six teams in the Champions League, all in the group stage. They have their four regular teams, an extra fifth spot, and a sixth if Atalanta or Roma wins the Europa League (and finishes outside the top five of the Serie A table). Meanwhile, Scotland gets one automatic spot. Same with Belgium, Netherlands, Austria, etc. It’s not as fun to watch when it’s the same teams from the same leagues year after year after year.