TFan made stuff has been around forever, and what is wrong with it?
Nothing, at least, for the fan that made it.

'Variants,' that might be applied as diversely as from one scenario to another, were an expected part of wargaming and stayed an expected part of D&D for quite a while, all through the 80s, at least, I'd say.
2e produced so much material that I suppose players accustomed to it might be excused for expecting whatever they wanted to play to have some sort of official incarnation, and the 3e-era lionization of RAW (and 3e DMs retreat into WotC-only and Core-only policies to defend their campaigns from the bloat), certainly took that from an expectation to a desperate need.
What is so magical about the WotC icon emblazoned upon a set of rules that gives it gravitas?
It's sacred to the Cult of RAW.
5e is trying so hard with it's push towards DM Empowerment, and rulings-not-rules to re-capture that acceptance of variants, including DM-specific and well-known circulating ones (such as Len Lakofka's in Leomund's Tiny Hut, or Steve Perrin's Quest Rules or so forth) like we had back in the day, and DMsGuild is evocative of the latter. A clearing house for potential widely-used variants.
But, AL monkeywrenches all that a bit, because it does stick to a limited set of options, and it is both a (re-) entry point for the hobby, and the easiest way for many to find games.
And, forums like this are also an obstacle, because discussions - and maybe this is still a 3e-era habbit that needs to be broken - tend to seem to gravitate towards the de-facto common ground of published rules or AL-approved rules.
That's all observation, no prescription for fixing it, though. Sorry.