Never pull out old mulch....it's ment to decay and add to the soil.
True, shrubbery is hard to kill but easy to make very very ugly for a very long time. Also shrubs are better trimmed down than trimmed up.
And in addition, the treatment for one shrub is very different than the treatment for another.
For rank beginners, it's safer and more economical to ask advice before performing surgery rather than after.
Please tell me there isn't landscape fabric or plastic under that mulch!
Most shrubs are best trimmed so there aren't "clippings"...that is not using electric hedge trimmers. That makes the center of the bush die out and gives you that awful green blob.
Blow out the dead leaves....or leave then where they are and cover with a new layer of mulch in the spring. That's what I do.
Linda C

Oh dear god, it's a terror of landscaping plastic underneath. I have found at least 4 layers, most is plastic, though some is the fabric. *blech* I dig out what I can, but it's just not feasible to rip everything out. I understand the mulch is meant to decay, but from what we can tell, this family has just been putting mulch upon mulch upon (plastic) upon mulch for the better part of 30 years, so it had spilled into neighbors yards, and outside the boundaries it should have been confined to. We pulled about an inch or two maybe out, until we hit the first layer of plastic.

We don't use electric trimmers, but we use like... manual hedge clippers, and trust me, there are plenty of extraneous clippings and twigs to be raked by the time we get around to all of them.

The electric trimmers are what causes the inside of the bush to be all plain twigs with no growth? I see that in a lot of our shrubs - I have to be very delicate with some of them.

I found this article, it describes my house to a t. The shrubs are like the landscaping at a bad corporate office, but I'd at least like to keep them healthy, and not have them take over/run into each other until I figure out what I want. I guess I'd been keeping them to the same shapes they were in when we moved in.

Any idea if I called around to nurseries in the spring that maybe they'd want some of these? Euf.

Here is a link that might be useful: Shear madness

Mulch over plastic and fabric will decay, but not "return to the soil". It will just sit on top of the dratted fabric and decay and provide a place for weeds to grow.
What you "should" do? Rip out all the plastic and fabric....get a knife and make slices and rip it up. Then find out what you have in the way of shurbbery and findw hat to do for each ( with pictures, you can find help here) then je juvinate the old stuff....and remove what is beyond.
It will be a 3 year process.....and a stinkin' job!...I feel for you! Might be easier to just sell the house?? LOL!
Also chances are huge that the shrubs have put out roots on top of that nasty fabric and into the mulch.....and that's a bear to re-do!!
You have my sympathy!
Linda C

The imagined horror of your landscaping draws me like a voyeur to a grisley accident!!
I read your link....yes that's what I was talking about. By creating a smooth surface ( they called them green meatballs, I call them dinosaur turds) you are shutting out light to the center of the bush...so the center is all brown and twiggy and the outside a thin shell of green. You need to break up that shell of green and allow light inside the er...ah....form! Some shrubs can be cut back to bare sticks and will sprout new green....some will die if you do that....so it's fairly important to know what you have.
Are they all evergreens? Or is there a chance you have some lovely blooming ( or might if given a chance) stuff in there?
First step is to do a rough ID on your stuff...evergreen, juniper, yew, arborvitae, azelae and Rhodo , deciduous and verieties... Pictures will help.
And might I suggest the shrub forum.
Linda C

Here is a link that might be useful: shrubs