You can use ADI-2 Pro/* as audio interface for small two channel setup, but it has never been designed to be a recording interface with TotalMix FX.
The ADI-2 Pro/* is the successor of a 2-channel AD/DA converter (the older ADI-2) and has been designed to be additionally phones preamp, USB DAC, DSD converter, etc (I think you know all the use cases from manual).
Mr Carstens told already in a few threads that the FPGA capacity of the ADI-2 Pro/* is full. See also the comment in the manual, that there are never enough FPGA resources from a developers standpoint.
And if I remember right the manual has already some notes that in DSD mode some of the features need to be turned off to preserve some processing power for DSD.
The reserves that are in the ADI-2 Pro/* are being used by RME for firmware/feature upgrades that are possible and do not overload the FPGA, based on own ideas and user feedback. Since over 2+ years we can see upgrades, which make the great product even smarter.
But if you need TM FX then you need to combine ADI-2 Pro/* with a recording interface which is designed to support things like TM FX and then also offers the i/o ports that you usually need on top for recording (Mic/Instr Inputs, some more analog inputs, MIDI, ..).
Vice versa it has also been said, that things like PEQ, dynamic loudness, high power preamps, etc won't be implemented in the normal recording interfaces. So these are unique features for the ADI-2 Pro/DAC product line.
As nice as it would be to have all features in every device .. think about costs. It makes no sense to design and release products that only very few people would / could afford.
Its better to buy two products that are both designed for a certain purpose and to be affordable, than to design and release products that will stay in the status unaffordable "dreamware" for most.
And it gives you more flexibility. The normal HiFi listener just gets the ADI-2 DAC, he doesnt need to pay for things that he does not require (TotalMix FX).
If people want to record the usual quality of recording interfaces is already at a very high level and full sufficient.
Here the people need more I/O that you would also expect from an analog or digital Mixer.
In both szenarios you can slowly upgrade and buy a 2nd device when you have demand and money for it and this gives you more flexibility compared having to spend much money just right now for one monolithic product.
UFX+, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1650v4, Win10Pro22H2, Cub12Pro