The story was the only good thing about BW1 (the post game was also good by modern standards but just okay compared to other contemporaries like FRLG, DPPt, and HGSS). In fact, I'll go a step further. It's really just the end game plot twist at N's Castle that's the only good thing about BW1.
BW1 marked a major shift in design philosophy for the series that was, IMO, largely for the worse, focusing on making the game much more casual and stripping away almost all sense of adventure and challenge. The region design became more linear, having a strict progression order with no alternate paths, no optional areas branching off aside from the odd dungeon or so, and minimal backtracking. Trainers had such short, easy rosters that you'd think it was illegal to carry more than 3 Pokemon. NPCs constantly interrupted you to tell you where to go and generally hold your hand throughout most of the game. Longtime sidequests and side content such as the Game Corner (which granted needed to be removed due to EU gambling laws but they didn't bring back Voltorb Flip or something equivalent), Safari Zone, Contests (which technically saw a spiritual successor in the Musicals, but failed to retain what people liked about Contests which was the move based appeals), and Secret Bases and QoL features such as the ones seen in regional gadgets were stripped away. Overall it felt like the video game equivalent of gluing training wheels to a bicycle, they wanted to casualize the game and force the casualizations down your throat. I've seen a lot of people complain about these things, but they falsely attribute these changes to XY. XY continued down that direction but it wasn't the game that pioneered it, that was BW1.
But BW1 had its own issues apart from the general change in philosophy for the series. Restricting the dex to only the new Pokemon was also a poorly executed idea. The notion of wanting to create a sense of discovery and wonder with a completely new set of Pokemon is a good idea, but when many of said new Pokemon feel like rehashes of older Pokemon, especially ones that we've seen frequently in past regional dexes, it undermines the newness that they were trying to go for. Replacing the Zubats and Geodudes that annoyed you in caves with new Pokemon that are very similar to Zubat and Geodude in Woobat and Roggenrola for example, does not make me excited to discover Woobat and Roggenrola for the first time. It makes me feel like they gave me Zubat and Geodude again without actually giving me Zubat and Geodude again. If instead of giving me another bat and rock Pokemon they'd have had a new bear or bug Pokemon inhabit Unova's caves or something, yes, that would've been very cool and made me feel like I was discovering new Pokemon throughout the entire game but as is it just felt like they didn't want to really have new, original ideas.
Storyline wise, yes the storyline was really good. But again, mainly because of the plot twist at the end where instead of fighting Alder, you conclude the Team Plasma storyline by capturing your dragon, fighting N with his dragon, and then fighting Ghetsis, who masterminded the entire events of the story. The storyline up to that point mostly felt like standard Pokemon fare and even a bit intrusive as I mentioned earlier. But overall, the storyline's climax specifically is the only aspect of the game that truly feels like it was a step up from previous games and in just about every other way the game felt like a regression for the series.