Wireless connections are always variable. Something as simple as a neighbor getting a new gadget (not necessarily even a networking gadget since these bands are unlicensed and accessible to anyone/anything.) Changing bands, or channels within bands may help. What you did is obviously a solution too. Wiring the house for ethernet is a more significant upgrade both in terms of the work involved and the benefits.
That said, yes the router could be performing worse, the printer could be performing worse, and you could have moved some furniture or just rotated one of the devices – wireless can be picky. Yesterday I was on the patio having internet problems, so I rotated my chair 90 degrees and solved the problem.
