I have been planting out veg and flower seedlings that I have sprouted from seed. I have to admit that I'm disappointed with the results: the seedlings are tiny and don't seem to be growing much. I suspect the compost.
I remember from when I first started growing plants from seed some 40-odd years ago, I would start the plants in seed trays, using a peat-based compost. Leeks for example would grow to pencil-thickness in the tray, ready for planting straight into their final positions, and African Marigolds would grow to 6 inches and would need the roots cutting into blocks to separate them for planting out.
Now, most plants seem to reach the stage of 2 true leaves, and then stop growing. I am hoping that my tomatoes, cabbages, onions, etc will recover from this setback, but I'm not happy. From now on, I'll be preparing my own seed compost.