Wi Fi is half the speed of the wired network

Had been having the same issue with internet connection going out for a minute or two in the evening on a regular basis.  Took the modem in and got a new one of the famed Model 37, the xFi Gateway.  Also replaced the coaxel cable.  My computer is connected by a CAT cable and I get 900+ speeds, however with my iPhone 15 Pro Max the best speed using Wi Fi is 550-580.  Shouldn't it be faster?  Was thinking of getting a separate high speed Wi Fi