Are you one of those purists, are you just making stuff up?
Because, so far as I see, most fans of the setting understand the need for mechanical changes because the rules are different, and they accept the need for changes based on societal attitudes. It's changes that have nothing to do with rules or a changing society that they object to.
For example, you could say "There are no wizards in Krynn". When Dragonlance was first written, there where Magic Users and Illusionists, but there were no wizards. That class did not exist yet. And then, when Dragonlance Adventures was published a couple of years later, it added a completely new class, unique to the setting, called "Wizard of High Sorcery". You could also argue that all Rogues have to take the Thief subclass, because only thieves existed when Dragonlance was published. This is all clearly nonsense.
The thing is, you can't remove something that does not exist. Ergo, Warlocks where never removed from Kyrnn because the class had not been invented at the time. Therefore, it's impossible to say "there are no warlocks on Krynn".
No. I'm not one of these purists. I'm in fact the opposite. A quick look at my posting history will reveal this, as well as in pretty much
every Dragonlance thread on this forum there are
always people whining about Age of Mortals and hoping they retcon it out. There are also numerous threads across multiple websites discussing how to handle the setting using the modern ruleset. It is well known baggage of the fandom (that and whether or not Kender should be allowed) and is frankly toxic behavior.
If a setting is so foreign to the rule set it's supposed to be played with that you ban 70% of the game, then one of two things needs to happen.
1. The setting must be adjusted to fit the rules currently produced. Including lore changes and retcons.
2. The setting needs to find a different ruleset that better emulates the fiction.
Silent option 3 is, of course, the setting is discarded and never spoke of again.
Thank you for agreeing with me. To clarify, I do NOT ban any option from 5e in my games. I change the setting and find reason why said characters exist. What I described was merely the 'canon' as established with the official setting.
More to the point on what you've said. They've already done this. It's called Age of Mortals. During which they did first try an alternative ruleset (the SAGA rules), and then ultimately released a 3.5 version that is considered the most recent version of the setting to date (well, not counting Dragons of Deceit). There is a
lot that got changed, but in essence they provided an in universe reason for why sorcerers/warlocks/bards (and again arguably rangers/warlocks/druids/paladins) exist, and advanced the draconians (the dragonlance name for dragonborn) to be more than just one dimensional villains who literally live to kill, fight, and do other things I cannot mention here due to forum rules. Even allowing them at the table during War of the Lance is
very problematic due to the rest of the world viewing them as savage monsters and would realistically treat them with severe scorn, which I somehow doubt WoTC wants to be the default for a base PHB race. (A few forum threads about orcs and even kender being stereotypes that were come to mind here).
Long story short, the fandom was split over it with much of the fans of the original trilogy of novels
hating every bit of it to the point of not reading or accepting any of it. These are the folks I would specifically label as "purists", many of whom frankly will not accept anything short of a full reset to war of the lance, and I argue the setting is worse off for it, because rolling back the clock for blind nostaligia's sake is all but incompatible with the 5e ruleset without making precisely the sweeping changes they wish to avoid.