you couldn't run a power network with more than 25% of your sources being either wind or solar.

The wind doesn't blow all the time. That means you have to be able to compensate power surges and declines using fast reacting power generators like gas and hydro. When you get more than about 20 % wind that becomes hard to do.

But this is really a pseudo problem. Wind is currently like 1 % of all power generated while even nuclear is just 15 %. That is, wind have to become bigger than nuclear power before we even need worry much about this issue.

Only Denmark has reached 20 % wind.

Peak oil is not an energy crisis. It is a liquid fuel crisis.