What would happen to the garden ecosystem if there were no more earthworms?

If there were no earthworms then there would be nothing which can convert the dead organic matter into "Inorganic solvents" which is used by Plants for their nutrition through the soil.
So, in that case, ecosystem cycle would not complete, & it will get disturbed by high amount 'cause producers will be affected.

Hope this helps!

Bc they get tired from playing with other kittens