No current modem is capable of 5Gbps. They all max out with a 2.5Gbps ethernet port. Maybe you mean 5Ghz wifi?
As for "fix and maintaining", that is what they are doing. Most areas have 2 downstream OFDM and 1 upstream OFDMA channel. They will be moving to mid-split soon for higher upload. That all uses HFC/coax though. They have upgraded some areas to fiber/FTTP(like in AZ) but that is very expensive and time consuming. They have to get permits and work with towns/cities for the upgrade. How are they not providing a service? Because it uses a different technology then you prefer? If you want fiber, check the FCC broadband maps to see what is available in your area. If nothing, move. When I bought my new house I only considered locations that had a fiber provider. Vote with your wallet.
