Generally, the intent is to be more specific than just 'thief' or 'barbarian'. Those are more concepts than Aspects. A lot of the design wants to push you towards using your Aspects, so having them too broad makes it easier to achieve things, and dilutes down the character concept. 'Horse riding' and the rest are good examples though.
That said, as long as everyone is on the same page going in, then you should be good. The worst case is if one person is making narrow Aspects and another is making broad, versatile ones. I'd feel frustrated if my aspects were 'climbing', 'lock-picking', 'sleight of hand', etc., and another player just had 'thief'.
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Thanks for your reply!
Yeah I definitely see what you mean. I'll play around with the idea a bit, perhaps reducing the amount of aspects if I include a broad concept as an aspect. Barbarian and thief worked great when I ran myself solo the other day, so I may revisit the idea with players.
Either way, I love these mechanics. :)