(Disclaimer: I picked the story up from where season 4 of the anime left off)

Overall not the worst story, but hardly the best. Heroes band together to defeat the big bad demon and his underlings, yadda yadda. The pacing felt very awkward though, simultaneously too rushed and too slow: the number of battles was very small, and it felt like the heroes moved onto the toughest enemies very quickly. We're made aware that months of training have taken place throughout the story but, again, not many enemies were fought, and all the Upper demons were defeated in a single battle -- which, conversely, was the part that made it felt as if the story went too slowly, since these fights lasted many chapters...

In regards to the characters: I liked Tanjiro as a main character since he was a bit different from other shounen protagonists in shounen I've seen. He had the typical spirit, empathy, and kindness of one, but was more disciplined and able to stop, think and plan out his moves in tough situations and battles instead of charging in headfirst and winning on anger and raw power alone.

Though besides him, I felt that, again, because of awkward pacing, it felt very hard to get too attached to any of the characters, which is probably my largest gripe with Demon Slayer. There's a LOT of characters to keep track of, which wouldn't necessarily be cause for concern if it wasn't for the fact that the mangaka seemingly doesn't know how to convey information about a character other than by endless, ENDLESS flashbacks to their tragic pasts for every. Single. Character. It was so much so that I could always tell when a new flashback about how their family was killed by demons, or how they were born into poverty was about to happen (or how their dead parent's ghost was about to show up to welcome them to the afterlife) whenever a character was dealt a specially hard/death blow. It got to the point that it felt like a very cheap way to try making up for the fact that the characters had either very little "screen-time" or just spent most of the time that they were around in one of the handful of fights in the story.

Even with Inosuke and Zenitsu... it didn't feel as their friendship with Tanjiro was that close, since they spent most of their time bickering (also, Zenitsu was possibly THE most annoying character I've seen anywhere in a long time) or in battle and (to my memory) didn't have many moments of bonding or vulnerability with each other. And finally, with Muzan, the main antagonist, while the final battle made a good job of showing his power and that fighting the Final Boss doesn't come without casualties or permanent injury, he ultimately came across as a weak character due to his lack of motive or backstory other than wanting to become the strongest and doing whatever he wanted to achieve said goal.