Three weeks (which I assume means three sessions) to get from 1 to 2 isn't slow at all unless the sessions were 12 hours each.
Most people stridently insist you're supposed to be level 2 by the end of the first session, two at most. And, again, keep in mind that I find 1st level mind-numbingly dull in a gameplay sense. A good DM provides or fosters a good story regardless of level, so this is exclusively a gameplay concern.
Also, that this is being raised as an issue at all (by others as well as you) gives me the impression that you see levelling up as a primary reason for playing rather than just a side-effect of other aspects of play - the roleplay, the story, the combats, and so forth.
If levelling is viewed as just a side effect then it can happen way less often without anyone caring much.
Nah,
levelling up is not at all a primary aspect of play for me. Having enough mechanics to actually sink my teeth into, on the other hand, is. And most 5e classes are barely deep enough to get your feet wet at 1st level. Being stuck in the "earn the right to actually be a thing" zone for potentially months at a time is very grating when you signed up because you wanted to be the thing, y'know? It's not that I care about levelling up itself. I just sure as hell don't feel like much of a Bard or Paladin or whatever until
at bare minimum 3rd level. So I care about getting those first few vital levels that are the "you must clear at least this much content before you're allowed to play what you want to play." Once that's out of the way, yes, I do want a reasonable rate of advancement but I'm fine with it taking 2 years to reach level 20 or the like.
And, as noted, a good (or even just decent) DM can provide/support a story that is engaging completely outside of the mechanics of the game. I am presuming that aspect is already fine. I play a role-playing game just as much to role-play as I do to game. If I just wanted to RP, I've been able to do that freeform for years and years, no problem. I play D&D, and other systems, because it offers both role-playing and
actual gaming. So...if I can get my RP fix by itself easily enough, and gaming by itself is a few mouse clicks away...my D&D kinda needs to offer a productive mix of both things in order to be worth my time. Otherwise I could just be playing Stellaris or FFXIV, or chatting on a forum.
If a very early TPK results in the group dissolving it probably wasn't much of a group to begin with.
What ever happened to persistence: "try again and let's do better this time!"?
Firstly...this comes across as really,
really uncharitable. Like borderline mockery. "Wow, not very persistent are you?" But assuming this is just an accident of phrasing...three things.
One, in a sense, you're 100% correct. As I've said many times now, I don't have a stable gaming group where I can
play. (My stable gaming group, I'm the DM of the one ongoing game I've ever run, and that's unlikely to change in the next couple
years.) I don't have a set of old friends I can turn to and say, "hey, one of you feel like running D&D?" All of my gaming was done online even before the pandemic, in part because I'm painfully shy, and in part because going to a physical game shop is rather a chore (I live in a moderately large city, the shops certainly
exist, but none anywhere close to where I live). And since it's not my friend group, I'm shopping around for online games wherever I can find them. So...yeah, an unexpected TPK is pretty likely to tank the group's interest in playing. Even when it IS being run by, and with, friends or acquaintances.
Two, unlike old-school play, I tend to go into a game with a concept I want to see unfold. I've invested a lot of time and effort into making that concept compelling and open-ended. Having that unceremoniously terminated, "you
LOSE, good
DAY sir," is pretty harmful to my enthusiasm and desire for play. It also means I must go to the drawing board and come up with an entirely new character, truly different from the first, all the while pining for what might have been. Yeah, I can get there. But I won't have much fun doing so. When "having a good time" is the whole point...and I'm already at least somewhat frustrated by having to slog through low levels I don't enjoy playing...it's just one more non- or even anti-fun element added in and one fewer fun element present.
Finally? TPKs are demoralizing as heck. They'll suck the air right out of a campaign. Even if it's 100% possible for the DM to realign and start over, it's hard on me as a player. Even just one character
other than my own biting the dust in an unexpected and unceremonious way is hard on me; I took the death of the party Wizard in my (lone, sadly cut short before its time) long-runner 4e game way harder than the actual player did, for example. Deaths suck, and severely damage my interest in continuing on. Total party kills leave me with a very strong aversion to continuing. Has nothing to do with "persistence" for me, it just is a majorly sucky feeling that has to be just accepted, neither really mourned nor worked through 'cause in a week we're supposed to be right back at it.
So...yeah. TPKs tend to be the end of a group, because I play these games in part to FIND a group that could survive a TPK if need be (but, assuming I've found one that actually works for my interests, the need is very unlikely to ever be such.)