"Fast lanes" have always been bullshit.
If you're paying for 100mbps, and the person you're talking to is paying for 100mpbs, and you're not consistently getting 100mbps between you, then at least one of you is getting ripped off. This reality where you can pay extra money to make sure the poors don't get in the way of your packets has never been the one we live in.
Of course, there are definitely people who are getting ripped off, but "fast lanes" are just an additional avenue by which to rip them off a little more; not a single provider who's currently failing to provide the speed they advertise is planning to suddenly spend money fixing that and offering a new tier on their suddenly-properly-provisioned internet, if only net neutrality would go away.
As Bill Burr said, I don't know all the ins and outs, but I know you're not trying to make less money.
Incorrect, and that was exactly my point
This is like saying that if the fruit at a store is rotten sometimes, it's not the grocer's fault, because the fruit had to come a long way and went bad in transit. The exact job you are paying the ISP for, is to deal with the hops and give you good internet. It's actually a lot easier at the trunk level (because the pipes are bigger and more reliable and there are more of them / more redundancy and predictability and they get more attention.)
I won't say there isn't some isolated exception, but in reality it's a small small small minority of the time. Take an internet connection that's having difficulty getting the advertised speed and run mtr or something, and I can almost guarantee that you'll find that the problem is near one or the other of the ends where there's only one pipe and maybe it's having hardware trouble or individually underprovisioned or something.
Actually Verizon deliberately underprovisioning Netflix is the exception that proves the rule -- that was a case where it actually was an upstream pipe that wasn't big enough to carry all the needed traffic, but it was perfectly visible to them and they could easily have solved it if they wanted to, and chose not to, and the result was visibly different from normal internet performance in almost any other case.