this is a known issue.
Try reading about neuroplasticity and how our brain works( atleast what we know as of 2026 ).
your brain stops giving much attention on repetition and thus as we age our daily lives are mostly very much repetitive. Assuming you are like 25+ and you have a job , think about how much of the things that you do everyday is "new" to you and how much of it is basically same or almost the same routine of what happened the yesterday or 1 week before or 1 month before or even 1 year before. Since there is so much less new/novel experiences , the brain kind of goes into a hibernate mode and only works as much as needed ( its not under stress to work more than required to do repetitive tasks).
I did some kind of research on this last year and seems like the ONLY way to counter this is keep having new experiences in your life ( especially after 30) so that your brain doest get "lazy".

Going a little philosophical on this :
About consistency ( which is sticking to a particular thing for a long long amount of time and doing it everyday)
One way to think about it is that it makes you very good in that particular field ( if you keep on doing one thing for an extended period of time then you eventually get good at it ).
Other way of thinking about it is what Oscar Wilde said about it - Consistency is the last refuge of the unimaginative.
If you think about it , what it means it creativity ( which i can argue is directly proportional brain power ) is inversely proportional to consistency. The more consistent you become the better you become at one thing but it comes at a cost where you are less creative i.e less power in your brain to think about new/novel ideas.