As I said, playing yourself is a subset of the agenda and requirement to play your character. If you are playing yourself, then injecting yourself into the character is entirely appropriate because that is who your character is.
What I am trying to explain is something that is difficult to put into words since it deals with mental agendas, intent and the ways in which we may seek a "buzz" or mental stimulation from roleplaying. If you are merely going to pick at the semantics in order to "prove" any view but your own wrong, then nothing I can say will change the situation, so I'll stop.
I'll simply state that I believe that Edwards did a good job in identifying three agendas that are clearly, once understood, quite distinct and self-contained (although they can be blended in the same person, and even in the same game, as Edwards said). I would be very open to anyone coming up with a fourth, but I have yet to see it.
One problem I see with Traveller sandboxing is that it seems to be "all Sim, no Gamism" - no XP to advance your PCs; not even a clear link between money and power since there isn't really gear or magic items that unlocks at particular wealth levels. You're expected to pretty much stick with the merchant ship you began with and your income goes to paying off the mortgage, ie you adventure just to maintain the status quo!
I think the lack of gamist reward cycles is what makes Traveller one of two truly pure Sim games, actually, and I like them both. The other is HârnMaster.
Play with both systems is interesting to me, because finding a good focus for Sim play can be tricky, as you seem to be saying here. I have generally found that it helps to go back to the source - exploration.
Pick an aspect or a specific to explore - in general terms this can be setting, situation, character or even system - and make it interesting, with some complexity and/or secrets to be found. Then let the players play and use the system to facilitate the exploration. I don't mean set up incipient conflict, necessarily (as you would to encourage Nar or Gam play), but just agree an interesting area to play with. Examples I have used:
- Traveller had an intriguing supplement called "Pocket Empires" containing Simmy rules on running a planet or a small empire. I set the players up as the noble "family" with wealth and resources in the "Milieu 0" setting, unpopular with the new Emperor and with every incentive to leave and form a private empire in the (randomly generated) space beyond.
- In HârnMaster, a small group of friends are all Shek-Pvar (mages) of some experience living in a wilderness "cottage"/chantry. One night one of them gets a spectacular blowback with some very "interesting" effects. The players play the characters who did not get the blowback, exploring their situation... (This was a one-off for a Con)
- The players play members of a military unit. The character generation system is used to generate missions that they are sent on, each one a situation to explore.
The focus is on the exploration itself, so it helps if there is something interesting to explore.