If you tried a different known good screen, then you probably have a failing touch circuit, and the touch ICs being the most likely (though not the only) suspects.
Search for "iPhone 6 Touch Disease" and you'll know what I mean.
Unless you broke the connector or pried something off the board, you have no responsibility whatsoever in this failure.
Because if the touch ICs themselves are failing, the reason is probably repeated drops or bends or sitting while the phone is in the back pocket. And/or the drop that caused the screen to shatter triggered or worsened the issue. All this caused the touch ICs to have connections that separate from the board, causing intermittent failures then no touch.
The most durable fix is to replace or reball the touch ICs, while repairing any potentially weakened traces. Then reinforcing the frame of the iPhone board to make it less prone to flexing.
This repair is certainly doable as any respected technicians has seen a lot of them.
But it certainly is not for a DIYer since you'll need very specialized tools and excellent control and skill to repair it. The touch ICs are packed close to a lot of critical components, and the other side of the board is populated by the CPU. Extreme care must be taken during the repair.
Some people place shims or electric tape between the board and the housing, to press the touch ICs onto the board.
This may constitute a temporary fix at best, but we've seen that it often results in failures that are harder to repair. This pressure is causing extreme stress on the board and causing traces to brake and more failures to happen.