Well I concluded you can't make everyone happy.
As well as the people who want a pony every level and the people who don't care one way or the other, its clear there are people who actually don't want stuff every level. Some of them specifically to piss in my Cheerios, but in among the old school flapdoodle there's a mostly legit complaint that in order to give someone a special ability every level, requires a game have a complexity above a certain level i.e. in most cases to give someone an ability to do something there has to be a rule that without that ability, they can't do it.
Admittedly 5E IMHO actually isn't too bad for this (rulings not rules and all that), there are a few places where they've stolen a basic ability and sold it back at an exorbitant rate like your ranger needing to get to Level 2 before his left hand gets a Strength bonus, but its not too bad. In part I guess they've filled up the progression by giving virtually everyone some spells, or equivalent usage-limited powers.
one of the problems with D&D's class model going right back to the introduction of theives and rangers is that there is a belief that every new class needs its own cool powerz and you need a class for every niche character idea.
So they could have introduced a tracking skill and you could get that skill as a fighter if you sold out something else, say access to heavy armour. Then you could have rangers without the need to generate a slew of new stuff for the new class thet then meant you needed a slew of new stuff for fighters to keep them at parity.
So the complaint about complexity growing out of too many class abilities is really one about too many classes with too many abilities more than it being about needing dead levels to prevent characters getting too complex.
I much prefer a simpler common pool of rather mundane powers and skills PCs can dip into as they level. 5E manages this approach with Feats rather well I think.
Add to this unique powers for individual PCs that come from the game world and i think you have the perfect mix.
All barbarians turning into bears at 8th level is no where near as evocative as your own Barbarian developing the abilty to turn into a bear as a gift for completing a quest for his bear spirit guide.
I know encouraging DMs to think outside the box, use their imagination and innovate is a litle radical and detracts from a clean corporate product but I am fairly sure you could wrap some rules round "Developing Unique Powers for PCs" as part of the DMG advice.