As previously discussed in other threads, basic GoGo service is fed via antennas mounted <mostly> on terrestrial based cellular towers. Row44 OTOH is fed leased spectrum from geostationary satellites in the Ku band.

This is why GoGo doesn't consistently work while an aircraft is on the ground (antennas mounted on the belly of the plane & cell towers not typically right on adjacent airport property).

OTOH, a satellite service such as Row44 is not intrinsically evil and is not (simply by virtue of being satellite-fed) inherently "slow". Certainly the satellite service providers can and do charge based upon how much space a given user is consuming at the trough. I have no idea how much bandwidth Southwest has "purchased" from Row44; it seems reasonable to think "not enough". Although it does sometimes work. Sorta kinda.

It seems unlikely that Southwest will discard their Row44 equipment investment anytime soon, especially after recently performing this work on 500+/- aircraft.

Much like your landline-based internet connections at home or the office, you can generally go just about as fast as you can afford to go with satellite. Usually. With Google Fiber in the final stages of constructing an entire new plant with fiber all the way to my house, I will admit a tad bit of bias