How easy is it to cut oneself with a serrated cutlery knife?

That’s a hard question to answer because it depends a lot on the knife. I think I can sort of answer with a few related thoughts though:
A serrated knife is jagged, therefore, it will require more pressure when dragged over a mostly-smooth surface to cut that surface.
A serrated knife will likely require less pressure to cut something when being pressed straight down than a non-serrated knife of similar quality.
Both of those previous statements are general, because it depends where the blade is sharpest along the pattern of the serrated edge.
Being cut with a serrated knife will almost always hurt more and be harder to stitch than a cut with a non-serrated knife. The cut will usually be more jagged, with more tissue damage and a greater risk of bone damage than a non-serrated knife (especially when it comes to fingers and other bones without extensive musculature to protect them.
All of these statements come from a combination of things my mother has said (she’s a nurse practitioner of many years so she’s stitched up a lot of people), and assumptions I’ve made from cutting a lot of meat while cooking. I’ve never cut another person – in fact, I’ve never even cut myself severely enough to require stitches. But if freshman biology in college taught me anything, it’s that pigs are supposedly pretty similar to humans.
As for how easy it is to accidentally cut yourself, it really, really depends on the knife and what you’re using it for. Serrated knives are not ideal for carrots, for example – you should chop those with a chef’s knife. Some serrated knives are more for bread, some are for meat, some are for soft vegetables, but the key to not accidentally cutting yourself is to own at least 4 knives: One for meat, one for bread, one for hard vegetables, and one for soft vegetables.
Always use the right knife for the right job!!! And if that doesn’t come intuitively to you, get a cheap color-coded set of knives at the store! You don’t need a pay a lot for decent knives, and you don’t need one of those huge sets – just enough to use the right knife for the right job. Knife enthusiasts may debate serrated vs. non serrated vs. recessed edge, and plastic grip vs. metal grip vs. wood grip, but you don’t need to do that. The average person is best served by just consulting the description on the knife package to determine which kinds of cutting your knife can safely do.

Wanbasion Black Stainless Steel Knife Set, Sharp Kitchen Knife