I think the difference is that you've been used to an environment where internal needs for improvements are addressed by a team you have close communication with, and a internal tools team (if you even have one), that services 50 people, instead of thousands.
Think of yourself less like a teammate of those team members, and more like a customer. If a customer wrote about your product like "I made a feature request, and they said it would take a quarter to implement!? I could implement it myself in a few days!", that would be unreasonable, right? You have a lot of customers, and you can't just directly implement every feature request without thinking about how it applies to other customers, not to mention that you have other work to do. That's closer to what your relationship with this team is going to be like.
Think of yourself less like a teammate of those team members, and more like a customer. If a customer wrote about your product like "I made a feature request, and they said it would take a quarter to implement!? I could implement it myself in a few days!", that would be unreasonable, right? You have a lot of customers, and you can't just directly implement every feature request without thinking about how it applies to other customers, not to mention that you have other work to do. That's closer to what your relationship with this team is going to be like.