Appreciate the frustration with a wifi network that is not responding.
Worth mentioning, correctly working, app will be highly responsive.
Why it can be troublesome in some locations, can be down to a variety of factors, including internal construction and nearby networks.
In my case, room to room for any radio device - mobile phones, dec phones et al, struggle to work. Across two buildings using back haul WAPs with a number of streamers on wifi and wired, no issues, incidentally BT FFTC.
If you are struggling then consider the following - no need to ditch BT imho, but a change of wifi may be necessary. Try some of the wise thoughts above from Tony and others. If not successful then unless you are so inclined to d-i-y, have a good sparky install a few runs of Cat 5 cable to a few locations - include a bit of redundancy but start with perhaps two WAPs back hauled.
To keep wiring simple, Router (eventually you would disable its wifi), by patch cable to a small PoE (power over ethernet, so power via cat 5), then patch cables to each of the ethernet cables. Cables installed into the house. Relocating router may make cabling easier, depends on your home.
Install WAPs where it is easiest - sparky will advise, with a socket and short patch cable to each WAP. Ubiquiti is a make endorsed by many on the forum. Requires a little care to set up but, fairly straightforward and will give reliable results.
There have been a number of posts where peps are reluctant to install cables, yet almost any house can have cat 5 easily installed if the house has central heating, running water and internal bathroom(s) - that gives a professional a few options and the runs do not need to be by the shortest route.
Ultimately it is a choice, struggle with trying to get wireless disks to work if all the advice isnāt successful for you or if you desire a stable home network, the suggestion is there. Good luck.