The USSR didn't so much as neglect its navy so much as have different doctrinal and strategic priorities. I would hardly call its massive expenditures on submarines neglect. The absence of CATOBAR carriers shouldn't necessarily be seen as neglect. The Soviet Navy saw its "carriers" as multipurpose hunter-killers to clear areas of NATO forces so that its SBBNs would have free reign. That's why the Kiev class had enormous suite of AA, ASW, and SS armament. Even the Kuznetsov had a suite of SS-N-19 Shipwreck ssms. They weren't to be used in the sense that the US uses its carriers, which is to project power abroad.

This is not to say that the Soviet Navy did not toy around with the idea of a blue water surface fleet, the problem was convincing Moscow that it was worth the additional expense.

A large reason for a neglected soviet fleet is simply based around geography. Into the Atlantic world there are few warm water ports that can be used year round from Russia. In fact if I am not incorrect St. Petersburg/Leningrad was the sole warm water port for a long time. Ports in the Black Sea were also not great candidates for a navy simply because the mouth to the Mediterranean is controlled by turkey. As such nuclear submarines, which would be more difficult to bottleneck, were considered a better tactical option than aircraft carriers.

An additional reason is purely tactical, the countries of the Warsaw Pact were by and large connected by land where the soviet military proved sufficient and no navy was necessary.