Ah, yes indeed it is.
I really like the fact they appear on the map and disappear dynamically, but that's about the only think I respect about them.
1) They are completely faceless, indistinguishable from one another. The difference is massive when compared with civ6, but even civ5 city states had several types of bonuses and a freaking little music tune after clicking on them, culturally specific.
2) They are extremely easy and cheap to integrate past the classical era.
3) There are no interesting ways to interact with them at all, you just throw the money and influence at them (which is the exact same problem civ5 city states had at launch, IIRC only later we got a lot of creative missions and ways to gain their influence and use them for your goals).
Being able to hire some of their armies as mercenaries is quite well done, I think, but otherwise I agree with you. That said:
1) The IPs do have individual traits that are intended to make them play differently, but they're generally ineffective at this purpose as things stand now. The individual traits for the IPs are there, they just don't do enough.
2) Agreed, way too easy to integrate and the process of doing so is too simplistic.
3) Implementation is failing the dev team's vision here. There are interesting interactions between you and the IP, but they're too subtle and/or buried. For example, your influence and your similarity to them on the ideology tracks affect your patronage of each IP. Also you have the ability to trade with certain IPs and not with others based on your patronage level.
[EDIT: forgot to mention that the patronage and absorption of IPs are also a source of grievances, so seem to be intended to be a big part of the diplomacy game between the larger empires. There might be more done that could be done here, however, to make these grievances stand out from the crowd of other grievances a little more.]
I'm speculating wildly here, but IPs are so bare-bones in their implementation, I wonder if fleshing them out is intended as a future DLC? This area of the game could use more flavour, for sure, though other systems are in greater need of immediate balancing, I think.