It does not have to be perfect, but i do not think it would be catastrophic either - it is mostly just turtle-ish forts without functioning army that will be harmed.
Speaking as someone who plays turtle forts without a functioning army, what you are suggesting would be a total catastrophe and would probably put an end to playing DF for me. I have tons of strategy games for when I want to have massive battles (which isn't very often), and it's not something I have fun with in DF.
maybe you forgot the talk was about leaving your fort alone and doing something else in the world without forcefully abandoning what you built up to that point. it does not mean you cant just play the same way you always did, you just wouldnt be able to return to a functioning fort after adventuring for a year or so, but you cant do that now anyways
That kinda reminds me, would the standing production orders not solve a lot of these problems?
I mean, you can already halfway automise the fortress during play if they'd exists. Too little booze? Make Booze. Too little food? Make food/trade food. Too little trading produce, produce trading products.
If you'd apply this to population demographics (always 10% military, 5% stoneworkers, 5% farmers etc.), burrow activation, and when and how levers should be used, you could automise the fort sufficiently for world gen.
Hell, if you could set this up for constructions and mining, a whole new fort building style could be created, where you design the fort, set up the automisation, and leave to adventure for a bit. When you return(and if you set it up correctly) your fort will have basically build itself. You would even be able to run several forts at the same time.
Regular dwarf mode will be more focussed on the fun micromanaging aspects(as the annoying ones will be macromanaged away with the standing production orders), like choosing the perfect wood cutter, looking for the HFS, dealing with foreign emmisaries and of course vampire cluedo.