The 'Averages a cup every decade' thing is a little disingenuous. Remember that Spurs Spent more than half of their time outside the top division prior to promotion in 1950. Since then Spurs won (ignoring Charity Shields):
1950s: 1 trophy
1960s: 5 trophies
1970s: 3 trophies
1980s: 3 trophies
1990s: 2 trophies
2000s: 1 trophy
2010s: 0 trophies.
2020s: 0 trophies (so far with 40% of the decade gone).
So since being considered one of the big clubs we have won an average of 2.8 trophies a decade until the point that ENIC took over, since when we have won an average of 0.4 trophies per decade.
I agree with some of your caveats. Though I will say that the scenario this year where Arsenal are reasonably likely to win the league (please GHod no!) would never happen under Levy as he would've dispensed of Arteta in 2019/20 when they finished 8th and if not in 2019/20 then certainly in 2020/21 when they finished 8th again.
Nearly every club has seen a similar trend due to the financial doping rise of city and chelsea. Think they've won 42% of trophies in the last decade.
If you looked at average league position. We're the best we've ever been.