AI kiting and turtling is not limited to slow capitals. It can happen even to fast, but not-too-fast, ships. I tried killing Remnant frigates with Wolf or Medusa, but they have similar or better mobility, and their shot range is not much worse than mine, plus their shields can take enough hits before I flux cap with my flux inefficient weapons. (I tried killing them with SO Lasher, but those with damage mods and no skills lack the flux stats to win the flux war.) Trying to kill them with some high-tech ships is tedious. On the other hand, I can deploy a Drover and murder them somewhat painlessly with Talon spam. Even Tempest has an easier time due to Terminator drone. (But if the Terminator dies too early, then it is about as hard as with other high-tech ships.)
This is why a little more than half of my fleet are carriers. Nothing outruns fighters. However, some tanks (usually cruisers) are necessary to capture points (carriers will not obey capture/control orders, only assault/defend), protect the carriers, and kill enemy ships that can destroy fighters easily. In endgame, if I do not use Paragon to murder things, I use Legion and sic fighters at the problem while I blast something else.
Re: Death Fleet
That was the point of soloing the simulator. If you can do that, you can probably solo such fleets. Failing soloing the simulator, try to kill everything in the simulator with your fleet.
Before 0.8, character with skills was stupidly powerful, and the enemy did not kite and turtle as much. Kiting started to appear in 0.72, but it was mainly limited to field boundaries. Now, the AI always kite and turtle anywhere on the field unless there is an obvious advantage, then they swarm and go for the kill.