One of the things that hurts Classic Traveller these days is presentation. Some things just seem a little dated or silly these days. Take for example the two staples of the Marines: the revolver and the cutlass.
Revolvers can be justified with one word: reliability. Revolvers are one of the most dependable handgun types in history. A Marine working in many exotic/deadly/alien environments might want a very dependable sidearm for a last resort. If we're talking high tech revolvers then you could probably drop one in liquid nitrogen and fire off a round.
I exaggerate. Don't do it. But you get the idea.
An Imperial/Colonial/United States Marine waving a cutlass around might seem silly. Au contrair. Marines frequently perform boarding actions. Boarding actions usually mean they're fighting close enough for the bad guy's breath to fog their battledress visor (of course the Marine is the good guy.)
Boarding actions also may be fought in areas you do not want riddled with bullets or plasma blasted. Shooting a plasma gun in the computer room of a ship being seized for intelligence is self defeating. If the opposing crew's armor doesn't put them in battledress' weight class a charge with cutlasses is not suicidal. A cutlass traditionally has a basket and hilt arrangement that works well as brass knuckles in a tight spot. You can cold cock someone and not run them through.
High tech materials can also make very scary melee weapons. Imagine the the psychological value of putting a titanalloy (or bonded superdense) blade through a door or hatch to announce your presence You might want to wear battledress for this stunt.
You can just call your cutlasses katanas. That immediately makes them cool. Just wear a back rain coat over your battledress and Traveller goes cyberpunk!
Once people get the hang of blades and get tired of stray bullets and beams wrecking their expensive ships a new arms race begins: broadswords, spears, halberds and pikes!