For me the forts are annoying because they, as they are right now, simply have to many negatives for next to no benefit.
Positive:
1. Gets rid of the old carpet sieging gig.
2. Adds tactical depth to war. To elaborate - I almost never had issue with figuring out how fort pathing works, sans few situations where it's outright bugged, so I rather like them as a mechanic to control enemy armies movements. But it doesn't mean it makes game more difficult, just different.
Negative:
1. There are simply too many of them in a lot of countries, prolonging wars that have clearly been won for no reason, other than "wait while game rolls dice for you".
2. Their maintenance is so high, that in early stages of the game I simply can't justify wasting resources so egregiously, unless it's of absolute importance, such as straits, choke points and defensive positions next to a major threat.
3. Encourage siege wars. This is when instead of actually fighting your enemy you re better off sitting with high siege general on a fort than trying to outmanoeuvre opponents army.
The issue raised by this thread in itself, in my opinion is not a problem, rather a symptom of one system having to deal with another system that doesn't work well, to the point where the only solution to keep the first system (AI) working well is to cheat.