When I try to write for Traveller I'm always pulled back by the "realities" of the Traveller universe. I think it's a rich background with which, in a gaming sense, to create any environment one wishes, but it's confining in terms of pure unlimited creativity by virtue of the fact that Traveller has now gelled into a cohesive unit unto itself.
Certainly there's a lot of truth here. Arguably, it's a major draw for folks that come here. But, the only thing I can see that's really stifling is perhaps the technology, but even then I'm not so sure.
If you don't go "munchkin", any new "discovery" is useful for everyone. Undiscovered alien technology is always welcome. Just be careful putting the 20g drive and high powered wormhole disintigrator weapons on the players starship. DO put it on, just be careful with it, like a +10 Sword Of Orc Slaying or something in D&D. That's the only real limit to technology, IMHO.
Now, if you only want to write large, galaxy sweeping story arcs, tightly integrated and involving the largest factions in the Imperium, then, yea, Canon can be constraining.
But, like I said, I think that Traveller is the small story writ large. And there's just an infinite variety of times, places, and circumstance players can be involved with.
Canon is just a backdrop, and frankly a loose backdrop, upon which to base your story.
How many "IMTU" stories do we have? Everyones TU is different.
Finally, of course, there's TNE which specifically addressed this problem by making the obliteration of Canon, well, Canon itself. You don't have to use the TNE rule set to play in the post collapse area.
And you can even have a post collapse area within the Imperium, before the Rebellion if you like. We have a single small planet here and we have every drama man has known playing out right here, right now. Greed, love, war, sacrifice, corruption, heroism, enlightenment, discovery, exploration, fusion bombs, bows and arrows, new knowledge, lost knowledge, etc. And that's just on this rock. Right now. Today! You're saying you can't find a spot in the Imperium upon which to paint your story?
The technology is, mostly, fixed in OTU, but that shouldn't stop you from adding your own. Look at TNE's FF&S. It had all sorts of tech that's not canon (powerplant and drives, mostly), yet that's an "official" supplement. Change your Imperium forever when the Klaatu of Epsilon Erandi V discover Stutterwarp and start, slowly, using the drive in commerce or warfare. Boy, that'll stir the pot in YTU.
Those are all great thought experiments and topics for expansion. How would it be used? Would it dominate space? Would the Klaatu become the Puppeteers of the modern day? Would the Zhodani try and steal and control the technology? Would the Imperium bribe their loyalty, or would some crazy navy admiral think it's too game changing and nuke them out of existence before they take the entire Imperium and galaxy with them. Become a great atrocity that school children are warned about in future generations, but, quietly, in the back rooms of power, They agree it had to be done. Shame the technology was lost. However, it is rumored there are a couple of ships left...