Ethernet throughput slower than expected

I just got T-Mobile home internet, and while throughput via wireless is blazing fast - sometimes 1.2 gbps - wired Ethernet connections aren't NEARLY as fast, peaking at about 70 mbps. Here's the setup.

-Two laptops, Lenovo 22H2SCMA00 and HP EliteBook 840. - Each laptop connected to its own Dell WD15 dock, which supports gigabit Ethernet. -Both docks connected to Ethernet jacks on the (home) office wall. -Cat5e from the office jacks down through the basement and up to another set of jacks in the wiring closet. -Patch cords from those jacks to an Asus RT-AC66U B1 router in AP mode; router supports gigabit Ethernet. -Router connected to adjacent Netgear GS308 gigabit switch. -Switch connected to brand new T-Mobile gateway, which supports gigabit Ethernet. I just realized I haven't tried plugging a laptop into the gateway directly.

I know going through essentially two switches isn't ideal, but I don't think it should be "take 1.2gbps down to 70mbps" either. I suppose I could unplug some non-essential gear from the switch and try connecting the jacks directly to that, without passing through the router.

Thoughts on where the bottleneck might be? Advice?