Signed an agency contract under pressure and now stuck with bad terms

Needed to onboard a marketing agency quickly to hit Q4 campaign deadlines and signed their contract without really negotiating the terms
We were behind on our launch timeline and the agency kept pushing that they needed signed agreement to start work. I reviewed it quickly cause terms looked standard enough and I signed to keep things moving

2 months in I'm realizing the contract is terrible. (18 month minimum commitment with auto renewal and 90 day cancellation notice) The payment terms are also worse than what we typically agree to The agency performance hasn't been great and we're locked in for over a year with very little flexibility to make changes or walk away if things don't improve

Finance started processing the invoices and the CFO noticed the terms are significantly worse than our other agency contracts. I'm now facing pressure about why I agreed to this setup and explaining that we needed speed isn't resolving anything

Is it worth trying to push back on the terms now or if signed agency contracts are set in stone?