Slow internet only in the evenings

We have had a problem that has occured over and over for the past several years with nothing but run-arounds. Every night our 2.1 GB service drops to zero - 900 mbps. All we want to do it watch Netflix on the TV, but there is little to no signal coming to our house. It affects the PS4, laptops, phones, Prime, and on the cable box we can't streak 4K Max, Peacock or Fox Sports. We call the the support person has us check the connections, reboot the modem and still the signal only gets up to 1100 mbps on good nights. They have swapped out the X1 router 3 times, Gen 2 Pods, Gen 1 pods, splitters and even a cable outlet in a bed room. The last guy told us the X1 was only able to recieve up to 1 GB and that we shouldn't be paying for 2.1 GB. Customer service thinks differently. The guy before that replaced a splitter in the garage and said a having Norton on a laptop that was turned off was creating problems with the firewall and we needed to uninstall anti-virus from all computers and cell phones. Each time they replace something and tell us it's fixed, but that evening it happens again. We have another tech coming out this afternoon to "fix" the problem. Many times we schedule an appointment and we get a call or message the next day telling us they located the problem and to cancel the appointment. This morning they even had me reboot the router only to get 1300 mbps so they are having an "expert" technition come out. Why doesn't comcast just admit they don't have the infrastructure to support the amount of customers and give us discounts on our service? Instead they just send people out to waste thier time and ours. Is there something I can tell the tech coming out that it is the speed to the house, not the speed in the house?