Not fast - Not reliable

Well, metrics do help explain the behavior some. There appears to be some noise that influences the signal quality. The signal strength RSRP -96 on the 5G is in the "Medium" range and the RSRQ -14 is in the "Good" range but the SINR at -3 dB is very "Weak". Both signals need to be improved, if possible, but the noise might be an issue. It might just be other signals in the area or some other influence in the area that accounts for the noise. 

The 4G LTE signal is weak so uploads probably stink. Both signals suffer from noise so performance is probably an issue. You can try different locations in your home to see if the signal metrics improve. With cellular it takes a little more effort to get it working in some situations. Your location might be on the fringe of the cellular range. Locating the tower(s) for gateway placement and experimenting a bit is really what it takes. If the 5G signal is on the n71 band that 600 MHz can travel out roughly 10 miles but being on the outer limits or having a signal that is degraded by trees, hills, buildings, etc… will impact functionality. With the PCI, physical cell identifier, you can find the cell where the signals are sourced from. Cellmapper.net is NOT 100% as they data there comes from users that post up to the server so if no one has contributed information on a given 5G tower it may not be seen. You can filter by 4G and 5G with the panel on the left and that helps reduce clutter in the results especially when there are lots of towers in the area. Of course you have to select the carrier first and provide location info to begin. Using cellmapper.net and Google Earth measuring for the distance and looking at the terrain between you and the tower helps see what is possibly going on. 

If the distance to the tower is say 3-5 miles and the 5G signal is n71 with an external antenna the noise could probably be reduced some but the antenna used and placement would take a bit of work. Yes it is not inexpensive to add an external antenna. I considered it but my cellular metrics are actually really good even roughly 4-5 miles from the tower but I have actual line of sight given the elevation of the tower and that our home is up on a ridge. Every situation is different and some are more challenging than others. 

You can run speed testing with speedtest.net and fast.com to better profile the performance. If ping latency is higher and jitter is higher it would not surprise me given the cellular metrics. Locating the signal source(s), experimenting with the location of the gateway, improving the cellular metrics, verifying the operation with the speed testing "tools" are really what it takes to possibly get a better signal. If T-Mobile is still working on the equipment in the area that adds frustration to the efforts. We had two episodes here in 2021 where work was being done on the tower/equipment and for days the signal was flakey. Once they upgraded equipment and got the programming dialed in the signals improved and became stable. I joined during the BETA phase in January 2021 so I knew there would be possible disruptions. I had no other reasonable solution here. I don't consider Hughes Net a reasonable solution. The only cable solution here is very limited for delivery and much more expensive if it can be had but everyone on the street that has it knows it is slow and unreliable. For a cable solution that is pretty lame service. I believe the cable here is over subscribed and old gear. 

The T-Mobile home internet solution may not be the best for your location but without some experimentation you will not know what is possible. T-Mobile or any cellular vendor cannot control the external factors for every single location. If you start to research cellular as much as I have you will quickly begin to see there is a percentage of users that are difficult or impossible  to provide service to. Sorry for the long response but hopefully it helps you pick it apart.