IMO the current CL has three big problems:
1) with the revenue gap so big, the group stage is pointless in half the groups (f.e. this season groups A, C, E and G). even further, winning the group hardly guarantees you a weaker opponent, which makes it even more pointless.
2) there are too many teams which brings down the overall quality of the tournament. If you look at the 16 teams that exited the group stage this season in CL, only Inter, Shakhtar, Ajax and United are teams I'd consider tuning in for as a neutral, so you have 12 teams that globally no one cares about, between them they have maybe 12 players the average fan has heard about, maybe even less.
3) even though it is true that there are too many teams, still some of the biggest teams in the continent are not qualifying for CL due to competition in bigger leagues being a lot more fierce. the Atalanta's and Lazio's making the CL over Milan is not the problem, both had a fun run in CL this season, Midtyland and Krasnodar making the CL over Milan is the problem.
The CL reforms might fix the first problem (even though I find the proposed format very strange), but they do nothing to fix the 2nd and 3rd, they actually make it worse by adding extra 4 irrelevant teams. The SL format may not be ideal (hardly anything is), but for me it gets a lot closer to solving those problems.