You will probably find the same problem happens during a desktop file transfer when Lightroom is not involved.
Wired networking is definitely much faster and more reliable than wireless. An Ethernet cable is a dedicated and fully shielded path that can maintain throughput over a relatively long distance. A wireless connection is subject to all kinds of interference: Competition with other routers and devices on the same band, noise, and performance that drops with distance and obstacles.
If your router and computer use the latest commonly available wifi standard, 802.11ac, the maximum theoretical throughput of that standard is 500 megabits per second (62.5 megabytes per second). But the maximum theoretical throughput of Gigabit Ethernet (available on most computers and routers now) is double that, 1000 megabits per second (125 megabytes/sec).
In practice, both are slower than advertised because you can only get those speeds under absolutely ideal conditions with the best equipment. And the problem is that because wireless has so many more challenges than a nice shielded cable, the difference (the drop in speed) between the theoretical and real world speed of wireless is greater than it is for wired networking. I have seen file transfers peak over 100MB/sec on my wired connection, but I rarely see more than 20MB/sec on my wireless transfers.
If speed is a requirement, it is definitely best to use wired Gigabit Ethernet whenever possible.