While I think it was fine since they fleshed out the characters and their personality thoroughly, and I got attached and grew to like them after spending time in the world with the characters, I could understand why others will be put off or burn out by its length and formulaic slice-of-life aspect with no real over-arching plot to tie them together. Though I personally don't think it has bad pacing or uneventful, just really long. The common route is great because of the fucking hilarious humor, Yuuji's monologues, and lively characters interaction with snappy dialogues. It's a long common route with relaxed pacing, unless people are reading with the mindset of rushing through to get to a specific heroine, in which a shorter fast paced common route would have work wonders. Overall, I think the length works for the characterization after all, and thanks to it the personality and peculiar traits of Grisaia heroines really shine through.
It's fine. I really love her personality and voice, and I think she's cute. But I can see why someone would think that she's annoying. lol