Russia has 50 nuclear submarines, of which 14 are ballistic missile carriers. Every couple of years they produce a new one, think its clear where the bets are on
I doubt it. The USSR / Russia concept of operations for nuclear missile submarines is way different from NATO countries. They don't typically conduct wide-ranging strategic deterrence patrols out in the open ocean. Instead they tend to stay in or near their own territorial waters, protected by surface warships and land-based aircraft. While US attack submarines have occasionally violated Russian territorial waters for special missions they don't do so on a regular basis because it's so dangerous.
Subs are very hard to track or to locate, which is why Washington has been deploying two thirds of their strategic warheads (the ones that are ready to use as opposed to being in cold storage or in disassembled state) on subs and why Russia, China, Britain, France and India all decided incur the substantial expense of deploying nukes on subs, too.
And not a single strategist on either side actually believes that to nullify the threat. A single boomer launching might not be outright MAD, but it would be too many warheads to defend against, and several major cities would be hit.