I quite liked the early episodes, but by the end I was fast-forwarding through it. It's a slice-of-life fantasy story, with very little drama and nothing that matters much. The characters are nice. Their interactions are mildly amusing. I didn't see much point in most of the episodes.
The heroine, Aizawa Azusa, worked herself to death at the age of 27 in her previous life in Japan. In her isekai fantasy reincarnation, she just wants to take it easy. She asks to be made immortal, then spends 300 years living a quiet life in a cottage. She kills slimes every day as a way of harvesting magical crystals to sell. Sometimes she makes magical potions and medicines.
By doing this for 300 years, she gets so much experience that she's maxed out her RPG stats.
If we went crazy and starting taking this show seriously, one might have issues with this, and other things. Did Azusa have any friends in her old life? Did she bother making any friends in this one? Why doesn't the show portray the weight of her former life and/or those 300 years? Or indeed any weight in anything at all? Why should this fantasy world run on RPG game rules, beyond the meta-reason of "that's endemic in anime these days". Why is this fantasy world equipped with equivalents of real things in Japan, e.g. soy sauce? Why are all significant characters female? (That's what the show's target audience wants to see, yes, but there's no attempt to explain it.) And so on, etc.
But we're not meant to be thinking such thoughts. This show is fluff. Inoffensive, happy fluff, but mostly pointless. (Incidentally, I have a theory that it someone was thinking of making it a fanservice show at some point, but the animation's so bland and tame that it has less impact than a falling leaf. The public baths, the occasional nudity, Halkara's boobs... you barely notice any of them.)
There's an understated theme of business and not working too hard. Azusa can be depended on to ban her friends from putting in the kind of hours she used to do. This is a good message to send in Japan. Also, our heroes don't tend to do conventional fantasy quests, but will instead start businesses and discuss how to attract customers. This isn't exciting, but it's at least distinctive.
The early episodes are okay, since they're introducing new characters and there's generally a bit of a story about that. I like the idea of slime spirits that want revenge on Azusa for killing 25 slimes a day for centuries. I also like ep.9 (a slime spirit turns back into an actual slime), since it depends on one of the cast's unique biology and so briefly stops the show from being generic.
Ep.10 is fun too, with a bunny girl minstrel who's into death metal. Our heroes encourage her to continue making her music, even though it doesn't sell, she's been doing it for 63 years and she's a failure who was collapsing with hunger when they met her. Hmmm. Things get more amusing, though, when they explain that her music sucks, advise her on a new artistic direction and say things like, "You have no musical talent, but that doesn't matter in this world! You can be successful anyway!" (Then, at the end, they colour their message by telling her not to give up completely on stuff that doesn't sell, if that's what she lives. She's found commercial success, but she shouldn't let that blind her. She doesn't have to enslave herself to the pursuit of what sells.)
On the other hand, I actively disliked ep.4, which becomes dull and trivial when our immortal, unstoppable heroine is beating up dragons. It gives almost no weight to a feud between dragon tribes, which means we don't care about Azusa's inevitable victory and enforced reconciliation. There's no such thing as a baddie in this show. The nearest we have is a pretty girl who's a bit silly.
I fast-forwarded through all fights, actually. There are more in ep.7. Sigh.
In fairness, Azusa's being voiced by Aoi Yuuki (Tanya the Evil and So I'm a Spider, So What?). I like her, but here she's trying to carry a world of marshmallow. Nothing has weight or serious consequences. Everyone will be friendly. This is soothing and you might perhaps enjoy this anime if you watch the odd episode, occasionally, when you've had a hard day. I wouldn't bother with it if I were you, though.