The problem is that you can’t really re-evaluate a transfer that is a bust and never sees the field, then goes somewhere else….because there’s nothing on film. And those are the ones that need to be re-evaluated the most. So the original ranking stands by default.
The rankings also totally ignore relative positional impact. A legit 4* QB that lives up to billing is 100x more impactful to the success of the team than a legit 4* strong safety. But they count the same in the rankings. I mean, Ole Miss just had their QB drafted in the 1st round, and their ranking is about the same. Pure nonsense.
They downgrade highly recruited players who don't see the field and then transfer to a less talented team. Many four-star high school prospects transfer as three-star transfer prospects.
Even without a lot of film, you can evaluate talent based on their inability to get on the field and by how in-demand they are in the transfer market. I have no idea how that factors into 247's metric, but it at least makes sense. Film isn't the only information recruiting services use.
It's not "pure nonsense". You just have to know what you're looking at. It's just a 10k-foot view of the roster talent. Of course, a good quarterback is more valuable than a good player at another position, but you can also step back and look at the overall roster talent.
A really good quarterback on a team without overall roster talent is going to struggle. At the same time, a roster with a lot of talent but a below-average quarterback is also going to struggle. Both can be true at the same time.
For example, if Arch Manning is a bust (I doubt it), Texas (the fourth-most talented roster) is probably going to struggle. At the same time, Arch could be the best quarterback in the country and probably couldn't take Vanderbilt (the 55th-most talented roster) to the CFP. Texas's overall roster talent simply means that if Arch is good, they are a contender to win it all.