You can not defend the Titan being the bottom four levels of Military tech. You're essentially trying to argue that a cruiser is more advanced than the final supership to end galactic stalemates.
You already can build capital ships with no previous research prerequisites, unlike cruisers, and surely, following the logic that titan >>> cruiser, then capship > cruiser too.
Anyway, IMHO the whole issue is with the final supership to end galactic stalemates approach. The devs probably wanted it to be this way, thats why the titans are bristling with weapons, which can be leveled and do terrible damage to fleets of smaller ships. I believe this was a wrong choice and its the sole reason of current arguments, whether titans are OP, come to soon, can be countered by other titans only, making the game predictable rush toward titans, etc...
IMHO, the titans should have been primary designed as support vessels, ofc with certain firepower, but not much bigger than your average capital ship. You may say now, supporting the fleet is already main role of the capital ships, so they would overlap here. I am not talking about various buffs and debuffs though, although one maa argue if you choose to build titan, you automatically give up on 2 capships with their supporting abilities....
What i am trying to say, just imagine Advent Coronata just subjugating enemy ships, suppressing them down and taking over enemy planets. Imagine Eradica just ressurecting your destroyed ships or perhaps even planets. Imagine Vasari Kultorask function as mobile phase stabiliser and able to mess with natural phase lanes (just an idea, nothing official)... the Vasari Loyalist Titan already works as mobile HW and can summon Dark Fleet ships, i was additionally calling for making its Maw ability to target planets... especially in case of this Titan its role as a warship does not make sense. Its supposed to be your capital planet after all, in which universe does it make sense to bring it into battle, when losing it means losing the game. Yet, this is how the game is currently designed.
TLDR: Titans would be perfect having just supporting roles, subjugating enemy fleets, overtaking enemy planets, stripping them off resources, replenishing your fleets, ressurecting destroyed ships.... no need for them to be designated fleet killers.