Marine is not my oshi but I really like her contents and have been watching her since her debut since she's a close friend of my oshi (Korone).
Singing is hit and miss, same setlist for the most part, but at least she knows how to use her voice to make song viral, couples with coomer bait MV for maximum outreach.
So-so when it comes to narrating games (depends on the type of games). Her horror game streams are pretty good due to her over exaggeration. She does really well when it comes to top down management sim games though. Her RimWorld streams are some of my favorites in Hololive. The rest are okay-ish, but Marine doesn't play game much nowadays. Pekora and Korone are better as pure let's play streamer I think.
God-tier zatsudan and improv skills. Prime sencho (pre-throat hurt condition) is the best vtuber you can have when it comes to hyping up a show. She can MC and role play with anyone and is very versatile. Look up some of her old clips (i.e. kindergarten roleplay, Mitsuhiko, pikachu, 3D) and you can see how Marine ran the show. Her banter with listeners are great to listen to even if she's not your oshi.
The best quality about Marine is her ability to navigate corporate politics. She knows when to push her manager to approve her projects, MVs, and in general her proactiveness and professionalism regarding Vtubing is very admirable. I think Marine and Polka are some examples of pushing Vtuber as a medium beyond just streaming karaoke/video games.
Her worst qualities are the inability to listen to her doctor, resulting in constant issues with her throat. Even during her supposed 'rest', she still went on to do recordings and strained her vocal cords. Overall she doesn't seem like the type that can take care of herself when needed. I hope this throat issue doesn't get any worse.
Here are some of my favorite Marine clips:
https://www.youtube.com/watch?v=FJltE4KGGLA&ab_channel=YumemiTranslationshttps://www.youtube.com/watch?v=v5h8QHlhje4&ab_channel=Craftarchttps://www.youtube.com/watch?v=rjVZZCeJ0CE&ab_channel=JShayTranslationshttps://www.youtube.com/watch?v=cWfHQwGGj6M&ab_channel=Tempura_EN 
