Most or all actual rebellions and civil wars work on a part by capturing the regular army's weapon and vehicle depots. Augmented by civilian vehicles (yeah they use freighters, point for that). But all armed spaceships seems vastly different and TIE fighters are never used by anyone except the Empire. The Rebels could or even should wear Stormtrooper armor (you can paint it or wear camo over if for friend or foe id.
Is there a canon explanation for any of that?
They definitely use captured vehicles.
Consider the shuttle that was stolen that allowed the rebels to land on the forest moon of Endor. Or the freighter that was stolen in Rogue One. This also seen in Rebels.
Later, the loss of A-wings led the rebels to steal an Imperial Quasar Fire-class cruiser-carrier above Ryloth with the help of the Free Ryloth movement. The stolen Imperial ship became their new fighter carrier and flagship Phoenix Nest. (Star Wars Rebels, Homecoming) - http://starwars.wikia.com/wiki/Alliance_Fleet
I think part of the problem is there are really only a few kinds of imperial ships. Capital ships, like Star Destroyers, Tie-fighters, and shuttles. Star Destroyers require 10s of thousands of people to keep them running. Tie-fighters do not have hyperdrives. Neither of them is practical for theft.
The Rebels could or even should wear Stormtrooper armor (you can paint it or wear camo over if for friend or foe id.
Stormtroopers are the faceless enforcers of the Empire. I can't see the Rebellion wanting to mimic or look like Stormtroopers. In a way you could say the Rebellion is out in the open, because they don't hide the faces of their soldiers. There is also something to be said for confusion on the battlefield, if everyone's soldiers are dressed the same, there is going to be a lot of friendly fire.
They do use them when they need to, like Luke and Han in the first Death Star.
Some just aren't practical to keep even if you seize them.
Consider what would happen were a small group of rebels these days were able to seize a Nimitz class carrier. Sure, they now have one of the most powerful surface warships ever created, but so what? They'd need carrier-trained pilots to use it most effectively, they'd need thousands of crew to operate it, they'd need a vast support infrastructure to support and deploy it...essentially, all they have is a huge white elephant. They're better off getting rid of it.
Original Star Wars movie "A New Hope" is based on contrasting esthetics.
On one side we have evil Empire, with its bleak wedge-shaped Star Destroyers, flimsy and bare-bone TIE fighters (not resembling any known earthly aircraft) and of course faceless stormtroopers and pilots (plus Vader). Whole look of Empire is based on fictionalized mixture of Japanese Empire and Third Reich from WW2.
On the other side are good guys - Rebels. Their main fighter X-wing has distinctly earthly look (wings above everything else, especially with foils closed ) , pilots look like US pilots, ships have more rounded and organic shape, soldiers have faces.
This contrast is not accidental, it is well known psychological effect that people subconsciously associate something familiar with good, and something strange and foreign with bad. In this case, with clear visual difference, Lucas didn't have to slow pace down pace of the movie to explain which side is good and which one is bad. From opening shots of Imperial Destroyer chasing CR90 corvette, and stormtroopers killing Alderaanian soldiers, we already subconsciously drew that conclusion.
Later however everything had to be explained, so we got somewhat un-plausible stories how Rebellion secretly financed and purchased almost completely different equipment than Empire, instead of just relaying on using captured stuff.
