No, I'm not. You may not see it, but it's very real. Traveller was quite incomplete at release.
Only if you use hindsight to declare what is "complete" and "incomplete".
Can you play Classic Traveller using the Books 1-3? Yes.
Can you play AD&D using the PHB, DMG and a Monster Manual? Yes.
Can you play Runequest using the rules from the core box? Yes.
Can you play Blue Planet using the Players Guide and Moderators Guiide? Yes.
Can you play Eclipse Phase using just the core book? Yes.
Can you play Rifts using just the core book? Yes.
Can you play Vampire the Masquerade using only the core book? Yes.
And so on. I'm sure you get the idea.
I would say all of these are "complete" games in themselves, because they're not missing the core material you need to be able to play them. Are they missing
supplementary material that help you play other things or that expand on what's in the core rules? Absolutely - but that doesn't make them "incomplete".
If Traveller's core was missing rules for combat and other parts of the game referenced those rules, then people would quite justifiably say "this game is not complete!". I know T5 has UWP extensions but it doesn't contain anything that describes what the UWP Extensions actually
do to anything involving trade or how they may feedback on UWPs. Hence, that is "incomplete".
"incomplete" means "it's missing components that you need to play it", not "it has what you need to play it but you want more". A game that has a combat system that only has stats for basic weapons (swords, axes, polearms, etc) isn't "incomplete" because it's missing some specific form of obscure polearm. A game that contains spaceships isn't "incomplete" because it doesn't have stats for a 4-man trading vessel or a lab ship.
It's actually fair to say that most games are released when "good enough to be played" not "when finished." Otherwise, we wouldn't see the raft of "Player's Guides" and rules expansions we see throughout the RPG market.
Again, I think you're using hindsight to say that. I think most publishers would say that a corebook is ready for release when they've got enough material for people to be able to play the game without needing anything else to play it other than a bit of creative effort. While some may deliberately plan to spread things out over "Players Guides" or other supplements (possibly because the core rules would be too big if it was all in one book), often RPG supplements aren't planned in detail in advance. Mongoose may have had the idea of releasing lots of LBBs for every career, but I'm sure they wouldn't have had any idea what those books would actually contain until they were written by their authors.
Very few games don't have rules expansions in supplements - Hero System 5E comes to mind as the best example of a "complete" game on that score, and T&T 7 is about as complete as it gets for T&T.
Sure, but that doesn't mean that games that have rules expansions are "incomplete" before those are released.