The Start Up spirit can conflict with what is best practice for a company of this size (related to compliance and risk related measure and mechanics).
Planning & strategic approaches are a little lacking when it come to operational changes (and even new processes) - there are times when scalability isn't considered or thought of (probably due to immediate reactionary application of certain measures).
Be prepared for 'hand holding' - it can sometimes be the only way you can do your job frankly. And, this isn't necessary a con (i.e. you will leave your mark!) - but, if you are of the mentality that coaching/guiding someone outside your team is not your responsibility (where you are irked and annoyed - and it shows), this may not be the place for you to work at.