To put more numbers to your point, lets take the 2021 Week 1 starters.not sure I agree with this when talking about quarterbacks. It's the one position that is fairly stagnant in terms of players (though the medium to low end players will play musical chairs)
2020 was five seasons ago, considering a 15 year career would be considered a long career, you would expect every five years to lose roughly 1/3 of your qb to retirement to be replaced by incoming draftees.
Here are the list of starters in 2020 that are no longer starting qbs: Tom Brady (retired) Big Ben (retired) Ryan Tannehill (benched) Matt Ryan (retired) Drew Brees (retired), Philip Rivers (retired) Cam Newton (benched) Jimmy G (benched), Carson Wentz (benched)
I probably missed one or two but qb is maybe the only position outside of kicker/punter where if you've made the leap to starting qb, there's a high likelihood that you'll still be a starting qb somewhere in the league assuming you haven't aged out.
Of the 32 starting QBs, their status is as follows:
- 12 Starting for the same team
- 5 Starting with different teams
- 3 Retired
- 2 Free Agents
- 10 Backup for different team
It could really be summarized as half of the starting QBs in the NFL are no longer starters after 4 years. Or to put it in science terms, the half-life of an NFL starting QB is approx. 4 years.