I didn't do well with brassicas this year. First lot of PSB got clobbered by cabbage white while i was away (even under fleece); I then bought in replacements from local nursery which keeled over with cabbage root fly; eventually grew some from seed very late, but they have now produced lovely spears, planted in large tubs, super limed & collared
Have just read the "Half hour allotment". An interesting concept and the author lists many plants which are recommended to be bought as plugs, partly because they're more successful, and partly to cut down on a space/time problem. They also enable forward planning and a degree of control over planting time.
However, they are expensive, and i think, not worth it for plants that can be easily raised provided you have a large enough space to gorw on in. Last year I bought in pepper plants - what a waste of money! Half of them died (they were from T&M) - this year I've raised so many from seed I had to give most of them away - yes they've taken over a windowsill, but they were so easy to grow I'd only buy in again if disease decimated them. So no, I don't think you've "sold out" - the skill, surely, is in raising young plants to harvest - whether they were "IVF" plants, or traditionally raised