Thatch formation is inevitable since it’s impossible to retrieve 100% of the cuttings every time you mow the lawn. And it's equally impossible to prevent dirt, dead leaves, and other debris from being carried into your yard by the wind and settling into the lawn. While you can't prevent thatch formation, you can manage it but removing as much of the cuttings as possible after mowing and using a dethatcher for lawns at least twice a year.
Also, go easy on the fertilizer. In most cases, the grass clippings left behind will break down and feed the soil so that nutrients can be absorbed by the roots which is often enough fertilizer. Adding more artificially may initially result in a thicker lawn, but when sunlight, nutrients, and water can't penetrate to get to the soil, you'll end up with more thatch than grass.