Another subject to ramble about. I will start with probably one of THE biggest lost opportunities, the Kievs. Four 40,000 tons ships (largest in their day after the US CVs) that were really useful as missile firing ships rather than carriers, simply because the Yak-38 was a dismal weapon.
A few words about the background. I'm sure many of you are aware of the projects for full fledged CVNs namely project 1160 and project 1153, discarded because they were too expensive. Also the soviets were perfectly capable of building catapults, they did had them in prototype form before 1980 and as i understand it a couple of sets were already completed for the Ulyanovsk.
So what could they have done differently? Historically they build 4 Kievs, 1 Tbilisi and one unfinished (Riga/Varyag) plus starting on Ulyanovsk, also 230 Yak-38s. But for the same money, a far, far better solution would be built four slightly larger Kievs (say 50,000 tons- they did had conventional carrier projects about this size at the time the Kiev program was started, they looked like a smaller version of a typical US CVN) with 2 catapults (hell, even one would do!) and about same aircraft/ helicopter capacity as historical (30-36). They could built 150 MiG-23K (which could be replaced by the MiG-29K in late eighties) instead of the Yak-38s, an aircraft which is light years away in capability compared to the Yak, probably at least twice the range with twice the payload, Mach 2, radar equipped and BVR capable, possibly leaving resources for say 50 Beriev P-42 AEW and ASW aircraft, or maybe it's development, the Korchagin Typhoon.
Alternatively, at least the Yak-44 AEW (and possibly ASW) development can be brought forward, historically they initially tried to have it operate from a ski-jump carrier by fitting it with four lift engines (!), that didn't work, tried to replace it with the An-74K, that was even worse, finally they went back to the Yak-44 concept and redesigned and refitted it with more powerful engines along the lines of the E-2C. I'm not sure if it could operate from a ski-jump Tbilisi or it was destined only for the catapult fitted Ulyanovsk and subsequent sister-ships.
So yes, for the same money and resources they could have had four successively improved and actually useful carriers, certainly more sellable (if the dissolution of USSR still happens), this would cancel the middle line Tbilisis, but they could have started on the larger CVNs like Ulyanovsk of 70-80,000 tons, able to operate the larger Su-27K and strike derivatives alongside the MiG-29K, they could fit it with 2 catapults and ski-jump if they wanted to (though probably as they would have had considerable catapult experience in this ATL, perhaps they would have fitted it with 3 catapults), whether they could have finished or not that is of course another matter.
If they really wanted to continue the VTOL development, the Yak-38 should only have been an experimental program, paving the way for the Yak-41 that despite it's complexity and cost was a capable weapon which could have been used on the Kherson class (and subsequent) LHAs, if they would have gotten that far (to build them i mean).