I would just like to add that the OP is over-reacting at 200/mil per hour.
I've spent the past 5 days doing these economy missions - 8 hours average per day - so to sum it up:
Time spent: 40 hours
Credits earned: 1,950,000,000cr
Average hourly earnings: 1,950,000,000 / 40 = 48,750,000cr p/h
In that time, I've only managed to get 3 factions Allied, 2 Friendly, and 1 Cordial.
Most of the time I still have some cabin space left because of time restraints, some of the time I get scanned and my missions fail (despite silent running / heat sinks), or time runs out and the mission reward is deducted by the passengers, and I have to put up with regular interdictions.
All in all, the credits per hour feels right for an end-game player like myself:
Combat: 47% Dangerous
Trade: Elite
Exploration: Elite
Yes, board hopping between Open/Solo/Private did or did not help - sometimes it's all down to RNG. I regularly found that I had no missions to accept for between 30-45 minutes despite board hopping. If I was lucky, both Open and Solo filled the majority of my cabins. A vast amount of systems fill the boards far more easily than the ones going to the other system to travel for ages.
These feel balanced for end-game and for my ranks, on a personal level. This allows me to buy all the low-mid range ships I haven't had the chance to try yet and will allow me to fully deck out a high-end ship - and afford rebuys.
I do not see a problem with these missions at all, and 40 hours is a considerable amount of time playing the game (doing nothing = boring). It isn't fantastic, it's a grind, but it is worth my time.
Ship used: Anaconda (all economy cabins except 1x 4 slot cargo rack for mission hand-ins to throw away reward cargo).