His voice is meh (I much prefer Matthew Broderick), but it's something I could get used to or at least live with. His delivery/acting is absolutely terrible though, and I wanna say it pretty much ruins the whole character. Simba's probably my least favourite character in the show. I feel like they did a really poor job with him. Yeah, his writing hasn't been the best either, but the voice acting plays a surprisingly big role in why he's so unenjoyable. I really hope Rob's voice acting and Simba's writing both improve in Season 2.
The Finnish dub has Simba's original voice actor (pretty sure he's dubbed Simba here in every incarnation of the character), and it's insane how much better the character feels simply because of his voiceover work. Not only is his voice more fitting as well as his acting better, but it really helps to have a VA who knows and clearly enjoys portraying the character, and also who fans know as the character. It was great hearing him sing Hakuna Matata again after all these years. Almost kinda emotional, in a way.