How much mulch is really necessary? Mulch is multi faceted. It covers the soil to prevent sun/wind damage. The carbon feeds the microorganisms that are feeding nutrients to your food. The decay from this process helps keep warmth in the soil to assist with plant growth.
What we need to consider is what is the mulch and where is it being used. Leaves are amazing, they create leaf mold which worms and veggies love dearly. They also create a lack of aeration which can stifle some plants, and start an acidity issue. Shredding them helps, but if you have a sticky slimy mess, it's time for a change. Maybe try straw in a wetter environment and save the leaves for the drier areas.
I also pull the mulch back from many of my veggies, especially root vegetables as all the plant growth is subterranean. Leafy greens are not affected as much, but you always want to avoid rot. Hope this gives you something to start your next mulching conversation with.