why is the delay on ship transfer considered to be an impediment to playing now that ship transfer is possible at all - when it was not possible for the first year and a bit of the game's lifespan?
Partly because after the first year of the game there was a big move towards encouraging specialisation of ship builds.
- enough mining equipment that a core miner and laser miner generally require two separate ships (or one very big one)
- higher-end combat scenarios that aren't really designed for multiroles, and also an increasing differentiation between "endurance" and "kill one big thing" combat builds
- engineering in general making modules less interchangeable / "just buy a new one when you get there"
- on the AX side different builds desirable for at least combat, sampling, Titan rescues and Titan destruction
- even cargo missions generally require a much larger tonnage than they did in those days, so multirole mission runners are trickier
- more recently, various things like Powerplay 2 or Colonisation with big progress bars balanced around "optimal" builds, so using the "wrong" ship is often very ineffective.
Partly because there's also more encouragement
to move around a lot
- Engineers only available in very specific places (a good set of pinned blueprints helps, of course)
- development of out-of-bubble settlement
- more recently, a much bigger bubble with Colonisation
Partly because Fleet Carriers essentially do give near-instant ship transfer (for longer in-bubble distances, barely slower than flying there and back yourself) and move your entire fleet and all your spare parts at the same time, so the existing ship transfer has gone from being "the only practical way to do this" to "really very clunky compared with a Carrier".
- sure, this can be viewed as "look, eventually you'll have 5B credits and can get both convenient transfers
and the ability to annoy other players just by existing" and all part of Elite's "starts off really hard, gets easier as you go along" difficulty curve.
- but it is certainly notable that the number of threads requesting instant transfers did drop off substantially once Carriers were released...
(Me, I don't care as such, I generally fly one ship and if I come across something that ship can't do, I solve the problem by not doing it because everything is optional. Transfers get scheduled for while I'm not playing the game so are effectively instant anyway.)