Literally the only demand made by the dominion was they stop going through the wormhole and making incursions into.their sovereign space. The federation has a neutral zone with the romulans that has lasted like 100 years or more by that point, but if there's a wormhole it's somehow their god given right to poke around someone else's territory? Not even to mention the Cardassian/Romulan pre emptive attack on the Founders homeworld. Prior to that they just sent spies and harrased ships in the gamma quadrant. Seems like a more than reasonable cause for war to me.
im going to have to watch ds9 again i think, i'm usually attuned to the anti-protagonist framing but i might've been genuinely asleep when this shit happened (star trek as sleep aid gang gang)
Similar gang except every second star trek series I rewatch is ds9 and so I watch ds9 5 times a year or so. I've watched ar least two episodes of star trek every night for over ten years now. I get off work at like 10pm and my schedule is have a drink, chain smoke weed, post work shower, eat, read, trek, sleep.