One way to make toplane more relevant
I'm sure there are many ways, but how about this: Voluntarily cancelling teleport puts it on a 20 second cooldown.
That's it, that is the entire idea. I'm sure you can see what I want here. Currently, we see a lot of people, even in high elo, use their teleport simply to get back to lane and not miss out on farm, instead of making plays on botlane etc. The reason for this, especially in solo queue, is that it's so incredibly hard to read how long your teammates will last during those 3 seconds of channeling that tp. So people don't use it to make plays, which is kinda sad.
Balance other aspects of it if you must. Maybe make the channel time 0.5 seconds longer or whatever.
I'm sure there are other ways toplane can be more relevant before the teamfighting phase, but I can think of no better start. How about you?