I wouldn't say it's useless, but the utility is reduced because we typically don't have the density of users where two timeslots on a single channel becomes a real limiting factor. A repeater that's set up for local talkgroups on one timeslot and then open access on the second is generally more than enough unless you have a lot of people trying to use it at once, especially in a world where anyone who wants to can have their own personal hotspot for less than the cost of a HT.
Also the usual "ham not HAM" thing.
This is wrong. 25kHz part 90 licenses are still available so long as the system meets the minimum efficiency standard (19.2kbps or better for 25kHz).
Y'all can use 25 kHz for repeaters? Here in Germany repeaters are 12.5 kHz only, allegedly due to a lack of free frequencies...
Here is the allocation for eastern New England for example: https://nesmc.org/docs/nesmc_bandplans_2023.pdf On the crowded 2m band we have 20 kHz for major repeaters and 9 kHz for smaller ones.
Leveraging dvmproject, dvmhost, and the FNE bits, hams can operate their own APCO Project 25 trunking systems with commodity MMDVM hardware and link them across the Internet. You can use various MMDVM boards, use a v.24 serial link to a Quantar repeater, etc...
https://github.com/DVMProject/dvmhost
Ain't nothing wrong in running a single voice-on-control channel simplex hotspot to experiment with P25, or link to bigger systems ;)