Your Verizon boxes are using a technology called MoCA 2.5 to communicate with each other over the pre-existing coaxial cables in your house. MoCA 2.5 is capable of 2.5Gbps under ideal conditions, but the left over coaxial cable TV, satellite TV, or TV antenna cable in most houses is usually not a great medium.
If installing Ethernet cable is feasible, run Ethernet! May as well pull Cat6a if you're pulling new cable in 2023, so that you have more options at 10Gbps and beyond.
If you don't want to do the home-improvement project of installing new Ethernet cables in your walls at this time, there are some potentially cheap and quick things you can do to optimize your coaxial cable tree for MoCA performance.
The first thing to do is to make sure you have a MoCA "Point of Entry" (PoE) filter connected at the top of your coaxial splitter hierarchy. Basically, this is where the coax cable from the cable TV company would come into your house, which is why it's called a "point of entry" filter. Putting a MoCA PoE filter at the top of your splitter hierarchy helps reflect MoCA signals back down into other parts of the splitter hierarchy, which helps with what MoCA designers call "splitter jumping" or "splitter traversal".
Another thing that can help MoCA signal problems is to look at all your coax splitters, and see what frequencies they're rated for. That information is usually stamped into the metal body of the splitter or printed on a label. If any of the splitters (at least the ones on the coax cable path between the two Verizon MoCA devices) is not rated for all the frequencies MoCA uses (which is up to something like 2GHz, if I recall correctly), then replace those splitters with "MoCA rated" splitters that are known to handle MoCA's frequencies well. MoCA uses frequencies well above 1GHz in order to avoid interfering with cable TV and DOCSIS. Cable TV and DOCSIS generally use frequencies from something like 5MHz up to a hair over 1GHz. Older splitters might not handle frequencies above 1GHz very well, and are thus a problem for MoCA.
If any of the coax cables (at least the ones in the path between MoCA devices) are easily accessible/replaceable, make sure those cables are high-quality quad-shielded RG6. You definitely want to replace those cables if they're RG-59.
And of course, make sure all of your coax cables are in good condition (no frayed shielding, no poorly-terminated connectors etc.) and that your connectors are tightly screwed together.
If you only look into one thing to try to improve your MoCA performance, make it the POE filter. In the vast majority of homes that report unsatisfactory MoCA performance, simply adding an inexpensive MoCA PoE filter was the only intervention that was needed.
