^^
Game rule altering books always have a saturation point. D&D has every single book contain more spells, more classes, more feats, more items and more monsters. This pushes the game towards a maximum overhead and aggravates power creep, while also making material look more stale as time goes on.
It gets increasingly difficult to be excited about a given piece of rules when you are presented with at least 3-4 new classes every month. Only the most notable would stand out, and mainly just become more and more focused/specialized to eke out extra value.
Really, they need a fresh setting to flesh out with fluff books(lower sales, but significantly more sustainable), adventures and campaigns. Space out the rules heavy books to every few months, because
wallets need regenerationLet's examine one of the things that you said is unbalanced; teleportation. How broken is teleportation really in D&D? Well, tactical teleportation isn't broken at all, hell its so unbroken you can get it on a 1400g item. Really, only long range strategic teleportation is broken and not because of mechanical abilities but because it disrupts narrative flow. And the solution to this can be as simple as not allowing long-range teleporation to work on places you haven't actually physically visited before. Otherwise require physical LOS to the location you wish to teleport to. Bam! No more using Teleport to end run around the adventure.
Its both more complicated and simpler than that. Qualitative abilities don't necessarily need numeric quantifiers, in fact, for the most part, numeric analysis fails because qualitative abilities are determined by the sum of their parts, how they interact with other abilities.
You can split them into Must Have(Required capability for a given level range), Nice To Have(Appropriate, but non-compulsory abilities) and Forbidden(abilities which break the plot/game).
Must have, going by the 3.5 model, is some form of flight, access to recovery(hp and non-hp conditions), planar travel.
Nice to have, are more commonly, tactical teleportation, senses, etc. Combat niches also fall under these(well most of the game does really).
Forbidden as mentioned, break narrative, or break combat. Long distance teleportation, Binding, extant Polymorph, etc.
Not so bad, as long as everyone gets some(and not all) of the mid-range capabilities.