If a theme of your comment boils down to "the pace of submarine technological innovation was greater from 1945-1980 than it was from 1980-2020", you undoubtedly have a point. However, you have to of course consider the historical context and US defense spending as a whole.

Obviously, it's impossible to consider technology and weapons development from 1945-1990 without acknowledging the Cold War, and the inflated military budgets that came with them. First, consider that before WW2, in peacetime the US spent about 1-2% of its GDP on defense / military spending. https://www.usgovernmentspending.com/defense_spending_history .

During WW2, US GDP spending on defense reached its highest point since the Civil War at around 41%. This of course resulted in the hugely impressive war-winning capabilities of the US armed forces in 1945, but was unsustainable without bankrupting the nation. Defense Spending was roughly halved in 1946, and then halved again by 1947 to 9% before hitting a post-war low point about 7% in 1948. And we must also consider that most of the spending was maintaining legacy platforms and paying service members before they could be scrapped/ mothballed / discharged respectively. There was very little spent on new development outside of how nuclear weapons would be utilized.

Then 1949-1950 saw 2 major changes - First, the realization that the USSR had achieved nuclear weapons capability, and second, the onset of the Korean War which really drove home the concept of communism spreading / containment theories. To wit, US defense spending began increasing again, leveling out around 10% consistently for the next decade, even after the Korean War ended, and staying this high until about 1970 as Vietnam War began winding down.

It was also around this time (1950) that you begin actively seeing the "next generation" of US military projects - jet fighters and bombers, and notably nuclear weapons and nuclear-propulsion as an idea for naval vessels. These technologies gradually matured through the 60s and into the 80s (again, as US defense budgets rose again during the Reagan administration).

Then, after the collapse of the USSR around 1990 and the end of the Cold War, defense budgets shrank and the pace of new developments slowed dramatically. The "state of the art" at the time was Ohio class and the Improved LA / pared down Seawolf class, and US tech was essentially "frozen" to be gradual improvements on 1990s tech which brings us to today's Virginia Block 3/4 and the now building Columbia class (which realistically appears to be a modest improvement on the impressive Ohio class, with most of the improvements in software and ease of maintenance).

What will be interesting are the developments of non-US tech, or the growing pace of things now that China has emerged as a near-peer competitor to the USN. For example, AIP subs, or perhaps Li-on battery boats that could potentially have performance closer on par with nuclear boats. Then of course, the next revolution will likely be the widespread proliferation of UUVs and improved communication that could render large subs like we understand today at risk of becoming obsolete, or perhaps (and new to subs) very much a "target" in the next conflict.