Weevils.

Agree with weevils as a good possibility for the last two photos. But I doubt that it is all the same creature (or issue) affecting all the other plants. The first one looks fine - it is just deciduous and has lost its leaves for the season....certainly not "eaten to the ground"!! I've also not known ferns (especially what looks to be a native sword fern) bothered by much....even deer ignore them, so possibly rabbits.

Slugs and snails can damage young bergenia leaves and weevils can munch on more mature ones. But neither will cause the plant to disappear entirely. If that happens, something else is at play.

btw, spiders are NOT garden pests and do not disturb plants. As they are insect eaters only, they are highly beneficial in the garden. Although I'd just as soon have them stay out of my house :-))

Weevil like chewing is visible in the first shot, as well as several others. And weevil damage to susceptible kinds of plants located directly beneath evergreen conifers - such as redwoods - can often be quite severe, much more so than with the same kinds located in the open.

So, how can I get rid of them? I doubt picking them off plants at night and dropping them in soapy water will get rid of them completely... how effective is using Diatomaceous Earth in such a severe situation? or spraying with Botanigard ES?

Is this a battle I can win on my own or should I call for backup? (i.e. a professional)

Once again, I am not sure it is all the same issue on all the plants. I have never known weevils to bother ribes or for that matter, just about any other deciduous shrub or tree with the exception of bigleaf hydrangeas. Also, because the ribes is not evergreen, it makes perfect sense to have lost all its leaves from "bottom to top".

But where treating for the weevils does apply, you are never going to get rid of them completely in areas with high existing populations and with plenty of natural cover. You will need to take a two-pronged attack, addressing both the larvae and the adult weevils. Beneficial nematodes are the typical suggestion for larval control and acephate for the adults. Nematodes are pricey and acephate is seriously toxic. Timing of applications is critical for both.

IME and according to most literature, larval damage is limited primarily to containerized nursery stock.......and heucheras :-) Adult weevil damage - the notching of the edges of the leaves you see - is only cosmetic and of seldom any harm to the plant. For that reason and because they are extremely difficult to eliminate, most homeowners just ignore them.

Snails and caterpillars usually eat the middle of the leaf first. Have you dug around under the mulch?

I have dug around, and haven't seen anything in the dirt. I did find a weevil across the yard from the ribes (see photo). If I leave them alone, is there a chance they'll eventually go away? I understand that some munching is normal, and I'm ok with a few holes here and there but it looks to me like this is too widespread. My concern is that my plants won't have a chance to just be. My four ribes are showing buds (!!!) but what happens when they open up? (see close-up photos of ribes damage).

Root and/or vine weevils are endemic where I live and many plants will experience leaf notching or feeding. And they all survive just fine except for the cosmetic damage. It is extremely rare for the larvae to actually destroy the roots and that is usually restricted to smaller herbaceous plants (like the heucheras I mentioned previously), seldom to any woody trees or shrubs.

You can treat if you like but it is costly and ongoing and many gardeners never bother.

Indoors and in containers vine weevils are another kettle of fish. They can and do kill plants by eating the roots. I wouldn't bother to treat outdoors but I would kill any weevil or larva I happened to spot.

Individual branches of shrubs may be girdled by adults and most of the circumference of root crowns of susceptible woody plants may be girdled by larvae. I have encountered this latter phenomenon myself on more than one occasion.

Landscape pests-Root weevil

https://pnwhandbooks.org/insect/hort/landscape/common/landscape-root-weevil