It is always a tricky thing when you want to use one game but a ruleset from another. Often the conversation starts with "Do you think X ruleset is bad then?" But that isn't always the case and there are only a couple of rulesets that I really do not enjoy. The factors that go into these choices are a lot more nuanced. Game designers have to chose a ruleset that they think will match the setting. Its style and pace. That is not often an easy thing to do. The ruleset also has to be commercially successful. It will not matter if it is perfect for the setting but everyone doesn't enjoy it.
I think the Shadowrun rules are fine. That wasn't the issue. It stemmed very much from why I RP and what I look for in a game. As long as everyone at the table is having fun it doesn't matter what style or ruleset you do. But over the years I have found I have become far more disinterested in rules. I play with some friends whose eyes light up in a crunchy ruleset combat. They enjoy the tactics and resource management of those combats. They love to chose the right feat/spell at the right time. It is a totally valid way to play. It's just not me.
I am the 7 year old jumping from a tree limb as if it were a pirate ships mast. Have at thee ya muck rake! Its story, narration and the players characters that excite me. To pull me into a different world, to have unexpected things arise and to see how the players create a shared story. A improv play with rules is what fires me and Genesys (7th Sea is another) is the best narrative ruleset I have seen. The dice pulls the players into story, it helps them add good and bad elements into every skill roll they make. it encourages the players to be descriptive and to expand upon ideas. I love Genesys.
Now there was a very important distinction which I hope people noticed. I said I felt it was the best Narrative RPG not the BEST RPG. Everyone plays for different reasons and different rulesets provide for different players and their playstyles. The ruleset that works best for me might not for the next player. Find the game you love and play that with other people that want to play that way and you should always have a good evening at the table.