Let's for a moment put aside the question what is an exploit and what constitutes a legitimate use of instant ship transfer. Let's just say anything goes, everything is legitimate, because most likely that is precisely how it will be anyway.
So it the fastest and 100% legitimate way to travel around in, say, an FDL is now to fly in an empty Asp with max upgraded 5A FSD (and maybe fuel scoop), then teleport the FDL to you. If you want to move about the bubble, anyone would cripple themselves by actually flying in the FDL and not in the Asp.
-> New travelling meta game: use fast taxi, teleport any other ship to the destination.
So you have found a good Sothis-style long range smuggling route. So you stack as many of these missions as you can. More cargo than would fit in the Asp, so let's take a Python, fill it to the brim with smuggling mission cargo. Deliver the goods, then whereever you are at the last destination, summon your taxi, fly the taxi rapidly to your smuggling hub, summon the Python.
-> New long range smuggling meta: fly the route back in a taxi, teleport hauling ship after your.
So you have found a good freeform trade route. A system is selling Imperial Slaves for fantastically low prices, and another system 80Ly away pays just so good. You go all in - trade Cutter, minimal shields, maximum cargo racks. Then you check what goods you bring with you on the return trip, and it turns out there is nothing too profitable for that leg of the journey. But hey! What if you made the trip back in just 2 jumps in your taxi, then summoned the Cutter? The saving on time is greater than any profit you get by hauling back, say, semiconductors, because every minute shaved off goes into moving more of these profitable slaves!
-> New trade meta: haul most cr/t cargo to destination, fly back in taxi, summon freighter.
These are just some of the obvious cases. A few weeks down the line and people will likely have discovered new uses for instantaneous ship transfer no one has anticipated. Almost every aspect of the game will be touched by it in one way or another.
And yes, it is technically optional, you could still travel in the FDL, you could still fly 200Ly back to the smuggling base in the Python, you could still move semiconductors on the trade return trip. But what before 2.2 was just natural now is a patently sub-par style of gameplay. You will intentionally cripple yourself by not employing the new ship teleportation meta.
And what a meta it is. Does no one of the people favouring instantaneous transfer see how massively awkward this will be once you realize for anything that requires travelling, you are better of with summon-switch-taxi-summon-switch? People say how annoying and awkward it is to use throwaway taxis to move their ships about without alway leaving another ship behind - it'll be just as awkward, just now you will feel compelled to do it all the time, everywhere, not just once in a while to park a few ships in a new location.