It's not a problem for the senior dev directly, but maybe down the road. And it definitely is a problem for the company once said senior dev leaves or retires.

Seriously, long term thinking went out the window long time ago, didn't it?

No, long term thinking didn't go out the window.

It is definitely a problem for the company. How is it a problem for the senior dev at any point?

What incentive do they have to aid the company at the expense of their own *long term* career prospects?