I personally don't really like the idea of tech trading, but I dislike disabling tech trading even more because of there is no way to catch up if you are significantly behind on tech. In my opinion, Academia is placed in a good spot on the tech tree because it allows you to catch up, but also doesn't allow for flipping techs (buying them from an AI, and then selling it to everyone else to make a profit, and a free tech). Of course after academia has been around for awhile tech flipping becomes a problem again. in my single player games I can keep myself from tech flipping, but in multiplayer games, there is nothing stopping someone from doing this to get ahead. Even worse in multiplayer games is when people intentionally swap tech between each other (essentially doubling their tech per turn).
How I would suggest to change tech trading is to run it through trade routes. If you have a trade route with a civ, you gain some tech points on techs they already have. For example, if you have a trade route with Russia that produces 10 commerce/turn, and Russia has Radio and Flight (which you do not have), then that trade route will generate 10 tech point (times a multiplier per tech based on how long they have had it researched) toward Radio and Flight. This way Russia can stop you from getting its tech by adopting a civic that reduces trade routes (or close its borders to you), but the reduction in trade route yield will in turn hurt its ability to generate tech points towards its own future research. This way of tech trading could allow the current tech trading mechanic to be completely replaced because civs that give tech through trade will get paid through the commerce of the trade route (perhaps civs with superior tech level would have more favorable trade route yield (through a multiplier that maxes out at future tech) so other civs will be more likely to trade with that civ).
While I'm on tech I also think that there should be an internet network national wonder (similar to telephone network) that generates trade routes in all cities (to signify the economic growth associated with the internet). If this were to be implemented "The Internet" world wonder should probably be replaced (to avoid confusion), with something like "GPS network" world wonder that grants all tech by researched by any 2 civs