You have a point, perfectly predictable games with the same chokepoints that you should try to hold game and a game again are far easier to balance. But it's not nearly as fun.
A dynamic battlefield where you have to actually observe the enemy and communicate with your fellow defenders about where the enemy is, in order to guard your objective is my opinion very "siegelike". Trusting that the enemy will always come from the same place is not something actual siege defenders could rely on, not with ladders, siege towers and covert sappers weakening your walls underground.
The battlefield is still dynamic, the options have just been limited to 2-3 options. The enemy will not go the same way
every time, they can take different routes to the flag. How you defend these routes can change the game. As an attacker, it is still very possible to surprise the defense by switching routes, and doing so with force. If the defenders doesn't keep an eye for this, they can get surprised!
Whereas it was impossible to observe the enemy with manual ladders, simply because there were so many routes! With 40 enemies on the enemy team, its impossible to tell who will be going where, and you often lost sight of them because of the walls and buildings. All this made almost always too dangerous to go away from the flag to knock down a ladder. Ask the HRE, they had one strategy: Camp the flag.
This is pretty much still how Siege plays out. Camping the flag is almost always the best strategy as you have maximum force where you need it and the enemy travel time evens out the spawn time difference. Furthermore attackers very often come a few at a time and charge a room full of defenders alone, dying almost instantly.
Only keeping the gate closed in a few maps is critical enough to warrant moving away from the flag.
It is still a viable strategy, but new options have become available. You can now completely halt the enemy offense at set chokepoints and
actually defend them! Rather than just defending flag and playing TDM. Chokepoints can, in some maps, be too weak, but in far the most maps it pays off to defend chokepoints.
and yes ozin is working on siege 2.0
it will include : selectable spawn points, progressive spawn points (example - capture first tier before unlocking second tier), adjustable round timers, adjustable spawn timers, adjustable door HP, ballistas (yep they fire through multiple targets in a line), etc
This sounds absolutely great! I just hope ranged will get a buff in this mode, as they seem UP to me in siege. (And while they're at it, nerf mauls in siege)