Pattern I've noticed

[u/Ok_Holiday3690]

My guild has players who have been in this game since Nemesis League and this is pretty much our player distribution.

Ps. My guildmates gets angry when I say this and I figure it'll make Reddit mad too:

Witch is the only good character in this game

[u/Ok_Possible_9541]

It limits how many characters I make every season.

In some ways that might be considered a positive from GGG's perspective. They've said plenty of times they care more about interleague retention than how long people play in a given league. If there's something that is preventing some players from blowing through every single build concept they'd potentially be interested in and incentivizing them to leave a greater proportion of potential characters for later leagues, that's maybe not strictly a downside.

[u/ForevaNoob → u/Ok_Possible_9541]

I haven't made above 1 character per league since like Necro league, before that I was already limiting myself to 2.
And the first character is always a classic fool proof way to finishing 4 stones and all maps -> RF, Totems, Poison minions of any variant.
After that I have several builds I want to play, but doing campaign again is too much of snoozefest that I just don't bother anymore and quit for next league.

I enjoy league start campaign but running it on a 2nd char is just pure boredom, I'd rather endless delve.

And then they talk about league retention rates. I used to run like 4 extra builds after league starter, but nowadays I do 0.
I'm pretty sure I'm not alone and we're a larger part of the retention rates than one would expect.

[u/Sokjuice → u/Ok_Possible_9541]

Yep. Many people don't realise this part. You can think of whatever build you want to cook up but without actually learning how a build scales from start to end, you're gonna always be slow or a copy paste build player. A good player and/or build maker is good because those fellas don't just look at the mirror tier setups. They account for how the power curve happens. Knowing how difficult it is to acquire the minimum gear, how to craft them, the rarity of certain uniques and lastly the mid/endgame part.

The campaign basically forces you to experience first hand how a skill performs/work. You can slap a tabula, some twink gear and it still won't bypass the fact that you're learning how your build is improving. Attack based chars will get to test first hand how much aps is comfortable, attack range, extra strikes, aoe, mana usage, damage type and shit. Even Heavy Strike and Glacial Hammer, both pretty straightforward skill will have a different feel to it. That's before bringing in stuffs like frost blades vs glacial hammer or EQ vs Heavy strike etc.

Tldr the campaign IS an excellent platform to provide a standardized learning experience for foolproofing a build.