TenForward: Where Every Vulcan Knows Your Name

The problem I had with Disco was their throwing out all previous Trek.

That just straight up did not happen. If they threw it all out then there would be zero overlap. There's an enormous amount and, despite complaints that have been made on other sites by other people, it is lore accurate and doesn't retcon any major events or technology. With the exception of adding a sister to Spock. Technically a retcon but explained why he never talks about her.

Costumes

A good example. It's a bridging line between the TOS uniforms and the ENT uniforms. You're starting to see more of the stylized look, more touches to detail but still holding onto that jumpsuit. It fills the gap in uniform design between Enterprise and TOS, it doesn't throw it out.

Set design

I mean, we've seen a number of ships in Starfleet that don't look identical. The set design also seemed pretty spaceshippy to me. Especially when you consider that it's an experimental ship designed for this one purpose. Very clean and pristine and showing that one purpose design.

Klingons didn't match TOS, TAS, TNG, DS9, Voyager or Enterprise

Even if you exclude DSC, Klingons don't always match. Then there's the Virus introduced in Enterprise that showed why they got kinda fucky in looks. We've seen them start shifting back to the Klingons we know. While they were definitely a departure from what we normally see, it wasn't enormously so. The skincolor was shifted, but the bone ridges and teeth were still pretty pronounced. They looked like a different type of Klingon for sure, but they still looked Klingon. Just more alien.

Spore drive wouldn’t have been rediscovered by anyone anywhere at the time of TNG?

Season 2 laid out explicitly that it is to be buried, forgotten and deleted. Demonstrated in the 3rd Season when even Starfleets own records show the Discovery as having been destroyed with no mention of the spore drive.

The Spore Drive was developed in secret by two men. One of whom died and the other was flung far into space. The only two ships with the drive were destroyed or lost. The only navigator lost and the tardigrades being unable to found as mentioned by Starfleet when specifically trying to find them. Then there was the existential threat of its existence with the Sphere Data. The ship, and the drive along with it, had to be deleted to make sure that the Discovery going into the future was protected from anyone finding out about that Sphere Data.

Literally no one was left in the development of the drive and the data on the drive was forgotten about, buried and forsaken to be spoke of by anyone by making it confidential at the highest levels. There was no way to rediscover the drive. You'd have to reinvent it and Starfleet only took a gamble on it in the first place because the Klingon war with Starfleet in its infancy made them absurdly desperate.