robject and aramis
You're both making very generic statements. Backing it up with examples detail might help.
No, I'm not - but I'll give you more detail anyway, because it's important to prove the differences are more than cosmetic.
Character generation in MGT isn't even all that close to CT. It was redesigned from the ground up. It's different careers, different skill list, and has different rank titles, even. Further, the promotion and reenlistment rolls are combined into a single roll, creating an up-or-out that is not present in CT, MT, TNE, T4, T20, nor T5. Plus, the special even roll has no precedent in any other edition - it does very different things from the MT and TNE special duty roll. Due to the differences in skill gain rates, MGT is close in level range to both CT and MT, but the skills themselves are not a close match.
Mainworld generation - which was unchanged from CT to T4 - is a different process in MGT - Starport is rolled with modifiers for population, unlike every other edition.
System Generation - CT Bk 6 is the prototype for the MT system; TNE adapts slightly from there, as does T4. Even T5 is an evolution of it. MGT's system generation doesn't include stellar data, orbit data (other than sequence from primary) nor much of the detail that all other editions have had.
Trade Systems - Traveller has 4 different trade systems other than MGT's - CT Bk 2 and T20 are close to each other; procedures are the same, but T20 has a larger table. CT Bk 7 is nigh identical to MT, TNE, and T4 trade systems; essentially, they're all the same rules. T5 is a 4th system. MGT trade is a fifth - it's not got the same detail levels nor rolls as any other Traveller edition. Nor is it even close procedurally to Bk2 nor Bk7. It's thematically closest to T5, but it's its own unique thing.
Ship Design -
While it's close to CT Bk2, it's far from the same. The addition of Armor, the small differences at the higher drive letters, the wider array of weapons.
And it's not just borrowing Bk5 stuff; either - it's doing stuff differently.
Ship Combat - The relationship between lasers and missiles is badly warped from CT's. CT Bk2 a laser does 1 hit, a missile 1d6 hits, and each hit is a weapon or a drive letter. MGT, a laser does 1d6 or 2d6, and missiles do 1d6; which is hull points of damage; essentially, each 4 points of damage also knocks out one system. In CT Bk2, a single hit from a laser cannot take out a ship's PP if that ship mounts a B or better PP, and in Bk5, it can't knock it out if it's PP2+; in MGT, it's very possible for a single laser to knock the PP out with a single hit. Likewise, in CT Bk2, a single missile impact is a major risk, averaging 3.5x the damage of a laser hit; in MGT, it's no more dangerous than a laser.
Meaning of UPP's: CT/MT/TNE/T4 size 0 is asteroid belt, LL has no restrictions on import technologies; MGT, size 0 is merely below size 1, LL has a specific restriction on both people leaving the starport and upon technology import.
Personal combat is different in every edition; MGT is no exception. Damages are not the same as in CT, nor is the methodology similar to either of the CT combat systems. (MT was at least ratings related to striker.) Damage taking is different from both CT editions and from MT. Unlike CT/MT, armor directly reduces damage linearly (in CT, it makes it harder to hit; in MT & striker/ahl, it indirectly reduces damage).
In point of fact, there is almost nothing in MGT which hasn't been changed from CT in some substantial way - ship design is the closest chunk, psionics the second closest.