LogMeIn performance where host is on AT&T Uverse Internet service

I used LogMeIn for many years and I have found, and this is true with another product I use, ConnectWise, that with all my clients I connect to, I have most using Charter, (Spectrum), cable Internet service: Those with AT&T, Uverse - which is a fiber supplied, over copper phone line to modem service, and they have plans that offer up to decent Internet service speeds but not close to Charter's, when connecting to AT&T clients when I used LogMeIn and now with ConnectWise the connection is so slow it is impossible at times to work with the remote host... Even though AT&T doesn't supply 60M service, maybe 25M, this is not because of the lesser speed (by not much lesser), nor is it the remote access product, LogMeIn, ConnectWise.... there is something else going on that has to be an AT&T design. With other cable clients - all is very nice and fast..., as with a few Dish clients I have. But  connecting to one client computer in an AT&T supplied office will slow down their entire connection with AT&T . Having someone on another computer run speedtests will show the AT&T speed just drops to speeds we saw in the 90's. All computers seemingly affected, by the one host connection... I see no mention of this so far in searching the Internet, yet I have been dealing with such for a few years...  this is obviously related to the host ISP it seems... anyone else stumble on this??? Going to AT&T with this question I might as well be talking to a rock...  and there should be no need to open ports on the routers or tweak the protection software firewall settings... for each host.