More access points is the only real solution. Ideally with Ethernet backhaul - mesh systems still consume spectrum which is what you're after - there's a finite amount of it (that you need to share with neighbors - especially on 2.4Ghz - and potential interference) and you need to maximize efficiency, so only use it for mobile devices that can't be wired - static access points (and other devices, TV, gaming console, etc) should be wired.
Mesh systems are a step up and can work but due to their cost (and also the fact it's usually hard to tell how well it'll perform without actually buying it and trying it out in the field) I would very much recommend just biting the bullet and doing it once and well with wired access points. A stop-gap solution would be to use powerline adapters to provide the Ethernet backhaul to the access points; you'll be limited in terms of bandwidth (mine top out at ~100Mbps in my current property, but went to ~300 in my previous one) but latency and packet loss-wise they're rock-solid and won't hog the precious Wi-Fi spectrum.
Forget consumer-grade crap as well, go for enterprise-grade equipment or at the very least "prosumer" grade such as Ubiquiti.
Mesh systems are a step up and can work but due to their cost (and also the fact it's usually hard to tell how well it'll perform without actually buying it and trying it out in the field) I would very much recommend just biting the bullet and doing it once and well with wired access points. A stop-gap solution would be to use powerline adapters to provide the Ethernet backhaul to the access points; you'll be limited in terms of bandwidth (mine top out at ~100Mbps in my current property, but went to ~300 in my previous one) but latency and packet loss-wise they're rock-solid and won't hog the precious Wi-Fi spectrum.
Forget consumer-grade crap as well, go for enterprise-grade equipment or at the very least "prosumer" grade such as Ubiquiti.