My 2014 Model S 60 has the same issue. From everyone I've talked to, the original browser in Tesla Model S/X was always awful. The only solution to this is that you will have upgrade the MCU1 (the original master control unit with the old processor) to the newer MCU2 (produced after 2018). I never use the browser because it's so horribly slow. Sadly, the Owner's Manual is only accessible via the same software interface. So, I'm having my MCU upgrade to the newer MCU2 with the Intel processor (scheduled for Feb. 20, 2023). It's MANY TIMES faster, from what I've seen. Plus it gives you access to Netflix, Hulu, Disney+ and YouTube. The cost quoted to me by Tesla is $1,880 (including labor).
My primary impetus for doing this (finally) was the loss of the 3G network. I've had to resort to using my phone's Mobile Hotspot and setting the car to "WiFi While Driving". This gets me connectivity, but it's a pain because I can only connect to the network when my phone is in the car. #FirstWorldProbems So, all the remote features of the Tesla App are useless without the car being connected to the Internet.
So... rather than have the modem swapped out (for $200), Tesla recommended I simply swap out the older MCU with the newer version. The service center will also replace the binnacle behind the steering wheel (mine is leaking). Contact your service center and see if they can arrange that for you. From everyone I've talked to who's had the upgrade, it's like getting a brand new car all over again.