So the original version did allow you to teleport to teammates.
It was also bugged. The bug was that it effectively stunned your ally while the teleport channelled - they couldn’t move, basic attack or use abilities. The day that they were added our almighty leader EdtheShred joined us in PBE testing - but… not in the testing discord. He played (as is often his wont) support Adagio. He rushed teleport boots (they had a lower cooldown at this stage as well) and kept porting to his allies to “save them”…
There was much wailing and gnashing of teeth by PBE testers who were killed by their ally coming to “help” them without realising he was killing them by locking them in place to be focused on.
The ability to port to allies was removed - both to avoid triggering the ptsd that many testers suffer after that match and for the reasons mentioned by others in this thread - it simply makes them too easy and too powerful. For similar reasons the cool down went up considerably.