Who's telling you that? Get some native wildflower seed mix ( a little goes a long way), rake up a few patches and throw the seed on. Costs very little so pretty much nothing to lose by trying.I'd like to "scrape" some patches this year and introduce some wild flowers for the wildlife but I'm told it's nowhere as simple as I may think, so trawling the web for ideas on how to do it......also looking for other ideas of what to plant. As I say not flash at all, just a little piece of privacy for nature to do its bit. Struggling for ideas at present. Oh bought a mini rotovator/Tiller to turn a veg patch over, jeez what a little brute. Best bit of kit I've ever bought.....far better results than I managed with a spade lol
I think there's a few specialist seed sellers who'll put together a mix if you tell them the particular conditions you have but it's a while since I've looked.