Wait, what? I don't get this at all. Obviously fireball is better than melee against a large group, but martials have clearly better single-target damage than casters in 5e. If your rogue or paladin is adjacent to the Big Bad but doing less damage than the wizard, they're doing something wrong.
5e solved the problem of "linear fighters, quadratic wizards" very nicely. So did Pathfinder 2e from what I've seen, but 5e did it first, so I'm surprised by this complaint. 5e does have flaws (like the magic item economy you mentioned, which is a gasping hole) but I've never found that to be one of them.
As I recall, the massive smite bombs were actually one of the few ways martials could keep up-- it's been a few years, so I don't have the calcs on hand, we started realizing it when we also realized that fireball was excellent single target damage due to them beefing it up due to its iconic status. The caster will do more damage than a martial in a round, which is supposed to be counter balanced by the martial's sustain, but as a practical matter forcing out a bunch of encounters to weaken the party as 5e encourages for its long rest and short rest balance mechanics, was difficult, even when we moved to an adventuring week via modified gritty realism rules. There were other strong spells too, fireball was especially egregious because it was written to be better, and there was almost nothing to it, it was a complete
First Order Optimal Strategy that doesn't fall off at any level of skill.
Under normal rules, if players aren't deliberately hobbling themselves and don't have a forceful time pressure, they end up resting according to resource drain meaning the casters had an incentive to play pretty aggressively, but if the time pressure is on, they generally won't even want to stop for an hour and the short rest classes feel even worse. Plus, around a table of friends, there's a general sense that if someone wants to rest, the other party members aren't going to fight them about it arbitrarily. We did push, but the 6-8 encounter mark is
rough, and we observed that it did take that much.
In a game that utilizes relatively accessible magic items, you had even more castings being thrown around (I know we banned the wand of fireballs and other casting increase items outright at one point) and I should emphasize that the number of encounters you need to burn out the spells was pretty high to begin with. This led to a scenario where it became very demanding to police the pace of any given adventure, and therefore to design encounters that weren't shut down by aggressive casting-- especially since spamming combat encounters to suck up resources isn't something the group generally enjoys, and the West Marches format at the time made it, so we couldn't wring multiple sessions of play out of a single rest.
I was active online, kept up with multiple blogs giving GMing advice, and while I could basically do a bunch of the stuff
@Oofta was talking about to make my encounters work (actually, I also really like Tome of Foes, the kobold press book, because the monsters just have a bit more bite) like, create specialized boss monsters that cheated action economy and stuff to be interesting and a threat, it was way too much work for me to stick with on a regular basis to negotiate session prep.
It also backed us into a weird corner where we wanted to get rid of SS and GWM because they made those two weapon styles much better than any other martial weapon style in the game-- and wanting to have active access to magic items made
not taking them much more of a newbie trap in our west marches, but they were also one of the few ways to drag back some ground. We actually had houserules trying to buff some martial styles (like I know the TWF's actual bonus was free, and then I think I built the effect of the TWF feat into the fighting style...) to try and get it where we needed it to be. I was actually pretty active on r/unearthedarcana because of the amount of Homebrew I was creating, and we were using, and for a little bit I thought that was the problem until one of our power gamers broke down what a bog-standard wizard could do, and pointed out which characters were even using any, vs. CRB options, their Volo's Hobgoblin Wizard for instance was RAW.
Add that to all the house rules and rulings I was making in general were reaching a significant volume, the lack of out of combat support, the relative dearth of character options that weren't part of a me curated Homebrew collection and other weird game breaking spells and items, and this decade-long GM called it quits. I casually grabbed the Pathfinder 2e PDF on launch day, thinking I'd probably wanna stick with 5e since I'd invested so much into it, and uh, it dragged me kicking and screaming over to Pathfinder with how well it addressed literally every pain point 5e had created for us-- to put that into perspective, I had vaguely resented Pathfinder for years from having started with and loving 4e and getting the "uhh you should be playing Pathfinder, it's just better than 4e in every way" treatment.
So,
speaking primarily as a 5e player who still hasn't played pathfinder 2e as long as I did 5e, that's my story, and in tandem with things I see out in the wilds of the community, is why I'm ambivalent about 5e's balance and accessibility. I think it back-loads a lot of its more user hostile elements, which is unusual for an RPG, and I think as a system, that might be its strongest claim to approachability. But I also think it's contributing to some serious salt build up by creating unhealthy pressures on the culture in the community.