That's rare. T-Mobile averages 53ms latency according to Ookla/Speedtest.net for multi-server latency. For wired connections, Xfinity averages 24ms, Cox 25ms, and Spectrum 31ms. So wireless does add an additional ~25ms of latency compared to wired, but 100ms is out of the ordinary.
Try the fast.com or speed.cloudflare.com instead. Ookla is pretty easy to game by the ISPs
T-mobile != T-Mobile ISP. For the better or worse, anything going through the ISP plan is bottom of the barrel. You can look through all the post on the T-Mobile ISP subreddit. Even those with 500 Mbps speed are close to 100 ms of latency.
This is interesting since I remember having much lower latency for 3G, perhaps < 50 ms, about 10 years ago. :) At that time, some of my friends were even using the home 3G to play games.