Yes, in general, having a better router would probably help (although you haven't mentioned the exact model you have, maybe it's already fine and the problem is elsewhere).
Enabling SQM [1] would probably mitigate the issue further, at the cost of requiring more processing power.
[1] https://openwrt.org/docs/guide-user/network/traffic-shaping/...
I didn't want to bog HN down in doing my tech support for me, but since you ask it's a TP-Link AC1200 (https://www.tp-link.com/uk/home-networking/wifi-router/arche...). I'm not doing anything meaty with it most of the time.
The solution's not going to be found in the firmware, is it?