Question for the Fruit, Veggie, Herb (NOT MJ) growers in here

Has anyone in here spent time actually breeding and crossing fruit, veggie and herb plants and even more towards taking hybrid plants and turning them into producing stable seeds that you can grow that kind of plant from.

I have tryied it but the seeds you buy are already hybrids & so if you try make hybrids with hybrids the seeds are not fertile. I did get a few to grow but ended up being mutants.

It's the same reason a horse & donkey can make a mule . But a mule can't reproduce