Even the path into the Death Star II wasn't an easy thing for the Rebels to get to; only two of the fighters managed to make it to the reactor without being destroyed.

Because we didn't see capital ships in ANH, and saw them gathering at the end of ESB and attacking in ROTJ, I had assumed that the rebellion had a much smaller number of big ships at the time of ANH - and the events of that film helped more rebel and add their forces to the mix. So seeing the big armada jump in during this film surprised me. (Even though I've played games like Xwing where there was a big fleet for game purposes).