And yet, without regeneration you will eventually whittle it down.
Well, you can chase it off. It outruns you, eventually, as very few things can produce it's movement rate. It has a con of 30, so it can go pretty much forever. Then, when you give up chasing it, it takes a long rest, regains all its hit points, and then does what it likes.
Oh, also, it can dodge. That gives you a disadvantage on the attack, which means you only hit when you roll *two* natural 20s, I believe. How much acid are you carrying? How much of the town do you sizzle into acidic sludge before you kill it?
On the picture it also does not have an opposable thumb
So? As if the artwork detail is going to be the GM's basis for what it can do when you try to pull that trick? Trusting soul, you are....
In any case, thumbs are great for small detailed work, but you can scoop up and toss things without them. And the thing in question is gonna be big - like, say, a cow, or an outhouse. It doesn't need pinpoint precision or a perfect football spiral when it is hucking cows at you.

nor does it look like it can lift its arms very high.
Remember that for the character's epitaph.