What is the make/model of all of your parts.
Likely, some can be reused.
Most games are graphics limited. Particularly fast action games.
Your I5-4690K is really quite decent.
Your most effective immediate upgrade would be the graphics card.
Try this simple test::
Run YOUR games, but lower your resolution and eye candy.
This makes the graphics card loaf a bit.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
If your FPS stays the same, you are likely more cpu limited.
A 3070(if you can find one to buy) should run on the same psu that powers your GTX970.
If you find that you are cpu limited, the first thing I would do is to overclock your 4690K. Some 25% increase in capability is available if you have a decent cpu cooler.
Your 8gb of ram is restrictive, that should be more like 16gb.
Otherwise, for a modern intel or ryzen processor upgrade, you are looking at a companion motherboard and ddr4 ram change also.