No, not 'only 77 edition'.
But the rules ethos I use are definitely 77 edition.
77 edition is not tied as directly to the Imperial setting and has a few options that are not in later editions
Skills and the Referee, jump drive not requiring a power plant, no link between computer model and jump number, jump message torpedoes, optional realistic displacement plotting in vector combat, trade lanes generation table - all of this is missing from later editions.
There is stuff from the later editions I do use - scouts and other (from MT) get two skills per term, whole damage dice for weapons, drive potential table, the range band ship combat system upon occasion, pulse laser damage. I have been forced to adopt the boon/bane mechanic from MgT2e because the players like rolling the extra die (no idea why) and they have to role play to get it so they put in more 'role play effort'.
Then there is the stuff I will never use - the Int+Edu skill cap 'rule of thumb'.