T20 is the best expression of the Bk2 paradigms.
AS to the "age of sail" feel: 400 years of a very different economic paradigm? 1500-1900, being generally considered the extreme bounds. Realistically, more like 1600-1800, still 200 years... and killed off not by the improvements in travel, but in communications.
In the US, demand based shipping was predicated upon both the 1880's telegraphs and rail and the 1930's highways. Things only moved when beyond local capability. Cattle moved east because of great surplus, not because of terribly great demand. Modern macro economics are predicated upon good knowledge and communications. Easy, steady, and fast communications. The third is NOT true of any TU not changing the rules mechanics. The second is not readily supported off the XBoat routes, since it's implied that such worlds get a weekly courier swap.... one in, one out.
The Roman Empire, decentralized as it was lasted a long time; 500 years. With similar commo lags, and similar local law allowances. What the Roman empire didn't have, was a lack of a shortcut for trade. Most roman trade took little time; one could ship from palestine and be in rome in a couple weeks, even tho' one could only reach the fringes by land in 6-8 months.
The Chinese empires maintained a relatively stable government for more than 2 millenia... with periodic upheavals.
The TU described by CT Rules is NOT a modern economy, tho' it has lots of them... they stop at the jump point. Not is it truly capable of becoming one without changing the rules.
The imperium, like any empire of persons, is not a perpetual institution. MT, while similar in setting, and in rules, it clearly different than the sole read of CT will produce. They are, to refute Hans, not the same universe, since neither the setting materials nor the rules produce consistent results with CT.
Nor, for that matter, is ANY edition of traveller the same setting as any other. They are close, but they are not the same. Even the worlds in the marches differ; in some cases, in their physical makeup. Typos? Perhaps.
The haphazard growth of CT, the focussed changes of MT, and TNE, and the way more haphazard growth of both T4 and GT really show us a huge range of different universes with a few common assumptions.
Bk2, like it or not, is the canonical means for CT small-scale speculation. It's very powerful at making money in certain conditions; conditions which some (Thrash and Hans) claim can't exist; canonically, they do.
Since CT is unlikely to be revised, and unlikely to be pulled, and still drawing new players, this issues isn't going away. Accepting the DGP changes as proof of Marc's intentions is as bad as citing Lennin's changes for Marx's intentions, or Stalin's changes for Lennin's intentions; it's done, and often, but is incredulous and erroneous, and leads to wrong conclusions. Unlike Marx and Stalin, we have a conduit to Marc: Robject.
It is pretty clear Marc's vision is NOT what GDW produced, at least not late on in the process. It's a hybrid of Marc and Loren, and even Tim, Frank, Joe, Gary, and The Brothers Kieth.
I like the autonomous dukes. I like the megacorps being little more than a parallel of Dune's Great Houses. I like merchants having to speculate in order to make the bills. It's good drama, and good fun. I could care less if it fits modern macroecon; modern macroecon also is leading us away from the values of personal liberty, basic human dignity, and basic compassion.
Traveller is humanism: a Man with a gun makes a difference. A man with a cargo changes worlds.
Bk2 allows a Man to Make a Difference...