Historically Fiserv's pay is pretty low. The bonus structure (below VP's at least) is not close to competitive. For example Managers get 5-10% annual bonus based on their salary. However Fiserv will then only give you a fraction of that say 85%. Then take that and split it half cash and half stock. Quite a few Fortune 500 companies give both stock and cash bonuses not split one tiny bonus. First Data was better at giving bonuses than Fiserv. However did the OFS people ever get bumped up to OFD bonus levels... NOPE. Where I am going with this is if you were remote you kind of accepted it. However if they want everyone in the office, they better start paying competitive as well. Although you know they wont.
Also good luck getting all of those developers in their 60's that are say 1 of 3 people that actually know the code on a given legacy app to move to those locations. They will be gone. Better start planning to migrate customers off those apps.
If you like going into the office, say you hate your wife and kids. Good for you, go. But understand it isn't for everyone and WFH employees can be very productive. Forcing an entire workforce to go one way or the other is pretty d-mb and shows leadership from an old man out of touch with the times.