Half truth. Be bold, experiment. I’ve been doing this for over two decades. Sometimes you get a weak cross, but more often than not you get something truly outstanding adapted to your micro climate. I have bred my own melons, cucumbers, tomatoes, lettuce, peppers, peas, beans, squash, onions, basically all the crops we eat. Some I have stabilized others I continue to add genetics. There have undoubtedly been failures but to me this is joy of gardening. Check out Joseph Lofthouse, landrace gardening for further info.