Nothing delicate, except looks perhaps, about any plant that grows in nutrient poor soil, surely! Those are the Survivors if they can thrive where even grass finds it difficult! One of my favourite flowers is the harebell. Very dleicate-looking but it grows in harsh places.
My 'lawn' is more moss than grass and what grasses there are are the kind of wild grasses people don't usually want in their gardens. Maybe that helps. I haven't planted or sown anything in it. Flowers have just appeared so I expect they seeded themselves and thrived during the quarter century when the garden was neglected. Perhaps many garden lawns are just too well cared for, de-mossed and so forth so the grass has taken over. I always favoured "greensward" rather than grass. Worked in my Oxfordshire garden too, though the wild flowers that thrived there were different from what does well in Argyll.
You have to expect things you don't want a lot of too, such as dock and sorrel.