Bro this can literally be soooo many things. Without a hardwire to check its almost impossible to nail down for sure, but glad to know my initial assessment appears correct.
Sounds stupid... but monitor your network and go turn on your microwave oven and then watch for ping spikes. Any high power devices, like appliances, power tools, may also factor in but at a lower rate.
You can also try assigning manual channels, which would be in your driver settings, to see if one frequency is more stable than the other. Theyre designed when on auto to pick the best one, but intermittent interference doesn't register in that decision. Just swap, should have 10 with the AC series. Could also switch to 5g mode if your router supports it, but I think the AC series is too old to, but that would cut off your allowed distance from your router pretty drastically in that range.
Ultimately bud, if you can't land line, we cannot rule out for certain that it's related to your wifi or your internet itself. You could potentially call your isp and have them check if you've been having connectivity issues, but what they tell you can't 100% be relied upon. Most of those people read from a script, look at a small segment, and have no idea what they're doing and make 12 an hour.
There's also the possibility that the antennae cable in your wifi card might be shorting out as well, or even thinning. That can cause issues as well over time.
Good news is those are like 40 bucks for a good one so pretty easy to rule it out.