1. Leafy greens don't need pollination. It's in your best interest to avoid flowering if you want product anyone will eat.
2. Very few food plants are dioecious, and the ones that are (like asparagus and dates) are either ones where the fruit don't matter or are not likely to be grown indoors
While #1 (and your general point) is correct monoecious crops still have to be pollinated if the product is a fruit or seed. The stone fruits for instance are monoecious with male and female parts of flower on same plant unlike marijuana or dates where plants are either male of female. But this isn't leaf crops as you mention.
In some species pollination occurs generally just with wind or movement (rather than insects), for example corn where the pollen falls down from flowers above onto the silks which are the female portion (sort of a vaginal canal if you will, i.e for every corn seed there is an attached silk). Or tomatoes which have closed flower and generally always self pollinate as the flower is blown or shaken with a very small amount of cross pollination on occasion. Pretty cools setup with these type of plants, massive reproductive efficiency through mostly self pollination but a little bit of crossing occurs as the occasional foreign grain of pollen gets from another plant so there is genetic variation.
You're right.. It's not some kind of laborious process though. Having grown all these things (except corn) hydroponically, the problem is heavily overstated. For personal production, you basically have to do nothing. For commercial production, you could turn on a fan.
