I don't think there needs to be one with as many as DL (quibble though: MK due to having a bunch more shows than DL is a lot closer in attraction count than you would expect by counting just rides) so much as they really just need to make each park have a larger amount of total attractions. This is particularly evident at DAK and DHS.
The constant replacement of attractions (e.g. in recent years Cosmic Rewind, MMRR, FAE, Princess Fairytale Hall, SWGE & TSL, etc) as opposed to building new additional attractions (less common like Tron and Ratatouille) has been a huge problem at WDW. Replacing Dinoland instead of adding Tropical Americas elsewhere is a continuation of this problematic trend.
Somehow at DL they manage to make additions without the "blessing of size" (e.g. SWGE, MMRR there)
SWGE and TSL gave us four rides replacing two attractions.
Also, we got expansions and reconfigurations which dramatically increased capacity: Soarin's third theater, TSMM extra track, a much larger foot print with Ellen->GotG, a 'green side' to M:S.
Not to mention that capacity increased simply by having a more attractive attraction (Ellen->GotG and Maelstrom->FEA).
I understand the longing for a brand new ride while keeping everything else the same. But, some attractions become less attractive over time (maybe not to hardcore fans, but to the general public). Not to mention have 'operational issues' that would require the expenditure of what a brand new rethemed ride would cost. This makes the calculus to replace with something less costly to maintain and more attractive to guests appealing to the powers that be.
Who among us hasn't demolished a ride in a theme park simulator that was no longer getting many guests and replaced it with something newer and better?
If it were up to me, I'd give DHS, DAK, and EP each three new rides to make them more ride-attractive while doing only replacements in MK to even them out. The BBTM new land drives me crazy... MK is at its infrastructure limits and they wants to make it more attractive? I guess that means park reservations for ever and much, much higher prices.