It's like Star Trek, around the time that humans build the first Warp 5 ship. There was an entire series built around the premise that NX-01 was the first ship to reach that speed, and then there were beings whose warp drives were capable of reaching Warp 7.There's lots of cool alternate tech. You can use Traveller to play a wide range of sci fi styles. The idea that Traveller is a game about the OTU is pernicious, imho. I've used Traveller for "Earth 2" type games where there were it was sleeper ships and no going back type colony worlds. I could easily see using the Naval Campaign guidelines to do a Star Trek-ish game, though that's not my cup of tea so I haven't.
And you have the Zimm drive in Earth/Clement sector games, Mindjammer's planing engines in that Traveller alternate setting, and 2300's stutterwarp just talking about published worlds that use the Traveller rules (or Cepheus, which is close enough as to no difference). Several of those games don't use fuel or change how fuel is used in major ways.
None of that is a problem at all. I would love *rulebooks* that covered alternate techs for other kinds of settings. But if you are writing for the Third Imperium setting (ie a sector book or other setting book, not a general Traveller rule book), write the stuff that fits that setting. Just like if you are publishing a Conan setting, you don't have laser pistols. Not because barbarians and laser pistols don't make a cool world, but because it doesn't make a Conan world.
So eventually, the humans caught up with those beings, and then surpassed their achievements.
Remember that the Age of Sail eventually came to an end, when people began putting steam engines into their ships and fitted them with iron hulls. Once they could do without sails, the new ships came to dominate the seven seas. By the time diesel replaced steam, sail-powered ships were already a memory.
1105 could be the first year the Imperium reaches the pinnacle of technology - the Hop drive. In the space of one generation, this will transform the entire Imperium, and the characters are among the first humans to own a ship capable of, not Hop-1, but Hop-2. And then they come across an alien ship with a Skip-3 drive ...
In other words, once you have the OTU in your hands, you can do whatever the hell you like with it. You can take the OTU in directions Marc W Miller and FFE couldn't even begin to imagine. There is no Imperium Canon authority - Traveller does not answer to the Vatican. Or to CoTI, or to lone grognards halfway across the world.