The question of whether it is true (or not) that
old[er] people [in general] loose the ability think creatively or formulate new ideas
would lead to a very opinion based answer and therefore it is not a fit for this site. Not everyone behaves or thinks in the same way. However, where this is true of those who are in this situation, there are several possible names for it and they tend to be cognitive biases. There is
The belief that a society or institution is tending towards decline. Particularly, it is the predisposition to view the past favourably (rosy retrospection) and future negatively.
The remembering of the past as having been better than it really was.
The tendency to defend and bolster the status quo. Existing social, economic, and political arrangements tend to be preferred, and alternatives disparaged, sometimes even at the expense of individual and collective self-interest.
Status Quo Bias
An emotional bias; a preference for the current state of affairs. The current baseline (or status quo) is taken as a reference point, and any change from that baseline is perceived as a loss.
In a self-justifying manner retroactively ascribing one's choices to be more informed than they were when they were made.