Only if you think you can win the war otherwise you are destroying the national infrastructure that your people rely on in a futile attempt to slow down one of the largest military forces on the planet which same said people will then land up paying to rebuild. The Russian military will over power as much of the Ukraine as they want in relatively short order and anyone who think otherwise is being naïve.
I don't think you've grasped the point at all, the Russian military can send troops into parts of Ukraine, holding vast chunks of it is another matter and destroying a bridge that a big column of enemy armour is in the process of using is a military no brainer... ditto to destroying an airfield you've had to retreat from, they weren't well prepared for it!
And again, these were bridges right next to Crimea it's quite possible Russia would seek to hold onto that territory regardless.
Honestly it's almost insane to be arguing that you'd be better off trying to save a bridge because it's infrastructure vs disrupting the flow of enemy armour into your country! These were bridges right next to Crimea FFS, that's not likely being handed back to Ukraine any time soon!