Compared to most other Targaryen men, he definetely came across as a saint. The ficitonal author was constantly full of praise for him. Him being a not so great father to his daughters is probably the worst thing about him that was mentioned. And even that was maybe a handful paragraphs in the multiple chapters about his reign. History books tend to be very kind to successful rulers like Jahaerys. I feel like there is more there. I bet GRRM has some twisted ideas on how he really imagined him to be.

I would have loved to see more of Jaehaerys purely because in the book he came across as such an amazing king and great man, that the showrunners/GRRM probably would have found smart and interesting ways to show that he wasn't as perfect as the book potrayed him to be. Same goes for his wife Queen Alysanne.