I heard it in Pre3e D&D tables and many games that replicated them.
It took a while for mages to get good and there were few ways to mitigate the restrictions.
All I can say is before WotC that was never my experience. Sure, people gripped about the first few levels with d4 HD and limited spell use, but once an MU or mage hit 5th level, things shifted. By 11th or so, they were powerful no doubt. Part of the balance was surviving those low levels IME.
I'm saying that the level of education and training for PCs has drastically increased.
I think more it is the shifting of views really, personally, but I see your point.
Look at the write up for the Fighter in 2024.
Well, right there is one of your problems...
It's beyond basic training. The D&D fighter is special force training. There is nothing between that are the Rogue's Super Shinobi School level training. There is no learning the basics and relying on the skills of your background, upgrading them as you go. You are going to an elite warrior program, mage training, priest tutelage, etc.
You can't even be just a town guard who goes for a score. The flavor for classes are just professionals, they are elite professionals. You may be novices at level 1 but you are all coming out of special forces programs.
In 5E at least this is the background IMO. By the time you get a leveled class, you are beyond basic training. A soldier background is basic training, a fighter is special forces out of commando school.
This would be more represented if backgrounds granted proficiencies like many homebrews do. Ours, for example, has soldier get proficiency in STR, DEX, or CON save, light armor and shields, two simple and two martial weapons, along with two skills and two tools and/or languages.
You combine that background with wizard, for example, and now you have a PC who is ripe for War Magic subclass for example.
This also allows you to foster the level-0 as race and background alone and gives you enough stuff to do without gaining special class features like Second Wind.
I guess I'm saying that there could be a class does minimal training, upgrades your background, and gives you a little more luck, grit, or fate to compensate.
Sure, a "survivor" class which is all about making it through the adventure with very limited features on the "proactive or offensive-side" of things but many more on the "reactive or defensive-side" where the luck, grit, fate kicks in to help keep the PC alive beyond simple "more hp"?
Is that what you're thinking of??
The Farmer gets Tougher and Tougher. Tougher than a fighter but doesn't know 30 ways to kill a many with 5 weapons. Just 3 ways to kill with a glaive.
The Merchant gets Luckier and Luckier. Luckier than a Rogue but less knowledgeable of skullduggery and no way as dodgy. They compensate for lack of speed with training with heavy armor and an axe.
The exSailor is no monk but packs a good punch. And he picked up a few water based cantrips and is using a magic anchor as a weapon.
These would sort of suggest that IMO. Or am I wrong?