While your general theme is correct, you missed [...] Endeavour
I was going to add a comment about that, but it seemed unnecessarily pedantic. My point was there was no ongoing manufacturing capacity. The same is true of ISS modules, and nearly every other program. Build one unit, stop, disband the team, destroy the manufacturing base, operate the unit for five to ten years and then ask "What next?", start a new system entirely from scratch. Pretend all the while that doing it this way saves money.
In general, however, I believe we should have started the design and production of a second-generation shuttle during the Bush41 administration
Waiting a decade to begin developing Shuttle Mk II is exactly why NASA sucks so hard. For starters, the first version should have been severely reduced from the ambitions of the actual STS, minimising the number of new technologies for the first generation. Building a 100 tonne space-plane in a single generation was completely nuts. The aim would be whatever you can build in five years, not one day more. Each subsequent generation starts the moment the last first flies. (With early design work starting even sooner.) So the second generation would have started somewhere around 1975, flying by 1980. Third generation flying in '85, fourth generation around '90... But I'm proposing increments that are probably a fraction of the ones you were picturing.
And just to be pedantic, NASA did start work on successors to the Shuttle in that period. So did the USAF. Giant SSTO spaceplanes, like NASP then VentureStar, which repeated every mistake from the STS program. Pushing the state of the art beyond reasonable limits, while insisting that there are "no show stoppers", under-bidding and over-promising, then blowing budgets and under-delivering. Then when you get cancelled, scream for years about funding and a "lack of leadership".
From the other AC:
MSL went significantly overbudget and overschedule. (Only the gob-smacking failures of JWST makes MSL's budget look reasonable.) But nonetheless, when it landed, people were excited... because NASA had "actually done something". Which suggests that not only are people excited about space, but they are starved for something to be excited about. It's worth noting that, unlike MER, Viking, etc, they built a single version of MSL with no possibility of a backup. Mars 2020 will be based on the same design, but again, will be a single unit. This is a trend at NASA. Like the 8 years between MSL and Mars 2020. Just long enough to lose most of the team, forget most of the lessons learned.
Similarly, not only did MER and MSL not carry any follow-ups to the Viking life experiments, neither will Mars 2020 even though "search for signs of (fossil) life on Mars!" is the centre of the NASA PR for Mars 2020.