I love your line of thinking. Lawns don’t feed the ecosystem, flowers do! But here in the US dandelions and clover are not a critical part of their diet. Native plants are the critical part of their diet - e.g. Native maple trees that bloom first!

Dandelions are native to Europe

Clover is native to Eurasia

They are far from the worst weeds, i wouldn’t go eradicating them like you should invasive plants (I leave both in my lawn anyways). But if we are looking to support our bees and ecosystem, then we should be re wilding our yard and growing native plants

In New England there’s a lot of neat spring ephemerals too (select from additional attributes)