Sorry I should have been clearer about the explore option. There is auto explore and you are correct that it requires a 3 star pilot. There is also manual allocation of any level pilot to explore an area. You just have to select the ship, click on the area of space to explore and select the explore option. Works on any sector that you have opened up and I have been able to get it to work on unknown jump gates and accelerators.I just bought and started in May, and I believe that there have been many changes relating to crew stats.
I don't know if you've started a new game recently, but I've been reading about experience, and all posts that relate to skill leveling/hiring crew with 3 stars seem to be from 2018.
Also, auto explore requires a decent star rating, and 1 star isn't enough.
It seems that 3.x patches have got xp to work however it seems that maybe they have been undone again in beta.