You have a soil issue. Unless it was an insect infestation.

Dethatch and core aerate. Remove debris. Too dress with quality compost and seed and feed. Compost, NOT topsoil.

If you’re in the Midwest, you’re right on the edge of seeding. But you can still dethatch, core aerate, and throw some fertilizer down at minimum. Then you can Dormant seed later, when soil temps stay below 40.

If you don’t address the soil issue then the grass will struggle.

If you’re more passive or want something less labor intensive, just having the core aeration done, then seeding and feeding will help. But, it’s gonna be a slower process to recover. Even if you do all aforementioned , it will still need cored and seeded for another season or 2.

And DO fertilize regularly. Modern fertilizers help amend the soil too.

In my zone, there’s a lot of clay. It gets compacted and causes moisture and nutrients to run off, and the grass roots have a hard time driving deep. The grass struggles and extra watering does nothing.

Focus on the soil, amending it and improving the growing conditions. If you do that, the grass will grow in, and eventually it’ll get thick. Throwing seed down in hard, unamended “dirt” won’t help. Seed won’t germinate well if it doesn’t get washed off or blown away.

ThisOldHouse YouTube has a playlist for Lawncare. There’s a video in there, a few actually, that are insightful, especially for the uninitiated.