I had a hilarious interaction with a Spectrum technician when I was dealing with an oversubscribed node with my home service (same issue you're describing here).

He was a line tech and was fully aware that my slowness wasn't related to the line, and as he replaced all the lines to my house he enthusiastically recommended that I report the company to the FTC and demand a refund for the service degradation which wasn't meeting their advertised speeds. He actually gave me great advice for getting my case escalated and I was refunded for several months on my service.

They eventually got the node upgraded (I was once struggling to get 60Mbps down on the same line I'm getting >1G on today), and they're upgrading everything to DOCSIS 4.0 currently. I'm not trying to sell you on them, just saying they'll likely work their problems out in the long run. Fundamentally, coax line connection's floor is Starlink's ceiling as long as the nodes are able to keep up.