Well yes, I got the best gear prior to the new stuff on my spaceship and I can't do the most difficult spacemissions. But I have several friends who can do them with much worse gear on their ships, I've seen them do it when over for dinner and such things. I'm just not good enough at keeping my ship moving around during flying. So yeah, having the best gear is no guarantee that you will be able to make the missions.
There are some people that have done all the space mission (up to the new ones) will out any mods (apparently - I've not actually seen video evidence just claims).
Unfortunately people BOTing can pretty much replicate this feat too.