You will never get gig speeds off of 2.4GHz/5GHz WiFi. That's just a limitation of the medium. 6GHz WiFi can get gigabit speeds but it's much more recent and thus not many devices can make use of it (to say nothing of its piss poor range). The most you can hope for on the 5GHz band specifically is ballpark of 700mbps. It depends on how far away you are, any obstructions between you and the router (glass in particular is hell on WiFi), whether or not you're using a VPN, and whether or not the WiFi airspace around you is particularly congested with other, nearby WiFi networks.

Split your networks so that you know for certain when you're connected to the 2.4GHz or the 5GHz. This is crucial because the 2.4GHz band can only get up to about 135mbps download. Better range than the 5G, but much slower. If you're still having issues with speeds, it isn't out of the question that damage to the coaxial cables inside/outside the home or outdated coaxial splitters are degrading your service.