Still rocking a 12.9" IPP from 2018 as well.  I have the 1TB, so upgrading to similar storage gets pricey.  90% of what I use this for is as a digital notebook.  The rest of the time it's a Podcast editor, and I relax with Logic Pro - both of which eat up the storage.
I hate that the accessories don't work.  I have 3x Apple Pencil 2s (one for each iPad and one that lives in my travel bag).  It's such as shame that these will be redundant if I upgraded the iPad.
Agree.  It's not about the money - I can easily afford this but I find it hard to spend this much on something with very little in the way of additional functionality over my current device. 
Poor trade-in values, and low resale for a 2018 device make this an even more expensive prospect than it needs to be.  Throw-in the fact that the pencil and keyboard accessories won't work with the new iPads and, well, I'm back to thinking even though I can afford it, what benefit will I get for the outlay?