I've no idea how you can politicise an inanimate object but if people/groups/organisations are willing to take credit for it when things go well, then they must also be willing to take the pantomime boo/hiss when things don't fair so well.
The new crossing was necessary and vital and although it could be argued that John Swinney was "getting on with the day job" when he signed it off, it was something he had to do. The FRB was barely 50% through its expected lifespan when recalculations of actual load coupled with projected wire failure meant the new crossing had to happen sooner rather than later.

As for closures, I've never experienced the FRB to be closed for more than 24hrs because of weather, joint/Union failure, but not weather. And 30 times in 2 years? I must have been driving over a different crossing,,,,
As One Day Soon alludes to above, they're bridges, nothing more, nothing less. The FRB done it's job, the newer QC will continue that job.
If it has to close for H&S reasons then so be it.

Neither of the bridges will come close to the original crossing in my opinion, the rail bridge,,,,s'pose we've got Gladstone's Liberals to thank for that 🙄