I wouldn't "disagree" with anything you said - and, for sure, the way to build and maintain a team/program is definitely by bringing in solid groups of freshman year by year.
But, unlike prior eras - where that was the route you HAD TO take - it is now all turned on its head.
Several programs (not just Cignetti at IU) have seen coaches come in, take over a program with just about ZERO quality "incumbents", and put quality teams on the field in year ONE, let alone 2 or 3.
You CAN do that now, if you have to (and a lot of programs have to - including PSU circa 2026). You can go into the portal in say 2027 - and essentailly recruit brand new class of 2023, 2024, 2025, and 2026 classes - by grabbing existing college players from the portal. That is, of course, a completely new phenomenon
If you have a staff that is going to make it happen eventually, they should be expected to show substantive improvement (nearly) immediately. If not, that is a very bad sign.
That wasn't the case pre-100% annual free agency. For example, when BGJ took over PSU in 2014 - and it HAD TO be built over a few years at least (and, lets be honest, he got things up to a high level quicker than any informed and reasonable person could have dreamed - - - his issues arose later

)
If the bulk of the 2027 two-deep is composed of guys currently on the roster (and the 2027 high school recruiting class), 2027 will be very very not good (could be worse than this year).
Back in the day, that is the group you would HAVE TO put out there. There were no other options.
But now there is no reason it has to be.