Those are part of the Bitcoin Core's code, your node doesn't need to have any of that if you don't want to and it's still Bitcoin.
Those are part of the Bitcoin consensus rules not just core's code. But it's true that you don't need to verify everything you be using Bitcoin. But you also don't need to download the entire blockchain if you aren't going to verify everything (it won't be a "full node" if you don't), maybe you should look into using a SPV client.
as well as nonsense usages of block space like ordinals and co.
Well whether you run a full node that can verify new features such as Taproot or run an old client that doesn't verify everything won't change the fact that the abusers will continue spamming.
the way as such experimental features are added on the most used node software.
Taproot and the Schnorr signatures aren't some "experimental" feature and it wasn't added to this software. It is a solid algorithm that is added to the Bitcoin protocol.