Whats your objective?
I'm thinking that you are probably right thinking that a hybrid bike can be ridden almost anywhere. If that's your objective, go for it.
If you are thinking that a hybrid can be almost as good as a real mountain bike for real mountain biking, you might want to think again. It's everything. All the little details add up to make a purpose designed bike better for it's specific purpose.
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My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.