In regards to conservatives becoming more radical over the past 20 years, I'd say it's more like 30 or 40 years. The radical right-wing movement seemed to start gaining some traction a bit before Reagan was elected. Reagan's election and the few years after that showed the largest shift. Radical changes since then have been more evolutionary than revolutionary...in other words, the shift towards radicalism has slowed since the 80s. Now, it would appear there might be another large push towards right-wing radicalism over the past few years, but it remains to be seen whether or not it will gain traction like it did in the late 70s and 80s.
Of course, I'm rather young and haven't paid attention to politics for many years. This is just what I gathered from historical policies and actions from the parties during those times. But that's probably a more accurate way to get information vs. someone's potentially/likely biased, maybe-affected-by-memory-loss recount of their perspective of events during those times.
One thing I'm fairly sure of is that conservatives in the 50s, 60s, and maybe through some of the 70s were more liberal than most Democrats/liberals politicians are today. The shift back towards right-wing radicalism more akin to that seen in the late 1800s and early 1900s has been a fairly slow process with some major shifts at times.
But, more back on topic, anyone who thinks a 200+ year old framework for any sort of organizational entity still applies today in its entirety is delusional and stupid. There are some core ideas that are relevant, but the Constitution as a whole is horribly outdated, inadequate, and has too many band-aids applied to it. Organizational entities that run the world, governments or corporations, need to do a better job sticking with the times so humanity actually progresses towards a better future rather than spinning our wheels in place or going through stupid, preventable positive and negative cycles.
Try running a relatively large business with a 200 year old framework that has had some patches and additions applied to it over the years. The core company values in this framework are likely still relevant, but your business will at least be horribly outdated and inefficient, if not fail outright. I know the government isn't a business, but the organizational size, structures, processes, and powers have enough similarities that the concept still applies. Frameworks need overhauls to fit the evolving world they operate in.