A third party router can help improve the stability of wifi connections since the ISP provided routers are always crap however a lan connection shouldn't see that much issue. If lan is down then the ISP is likely the one that sucks. If its wifi only thats down then the router sucks. But this isn't necessarily always the case.

I had massive issues with our shitty copper lines in britland where my bandwidth would slowly get slower and slower until it was unusable. I'd open a support ticket, they'd fix it after a few weeks then it would slowly start dropping again. Didn't matter what router was used the only thing yhat resolved it was when fiber lines got installed and I switched to that.

A third party router may make your wifi more reliable but wont do shit against actual outages. I have heard stories of virgin media routers being so crap that they themselves are the point of failure causing what would appear to be an outage.