carburetors and fuel pumps with rubber diaphragms will not stand up. There is no damage to the engine itself. fuel lines are not a problem to replace on small engines. The gas tank is in close proximity to the engine and the lines are easily accessible.
The problem is that the alcohol has a high octane. It is mixed into the fuel and falls out of suspension when it absorbs 5%(?) water by volume. Then your octane drops significantly and detonation occurs.
Actually, that's NOT the case. Especially in the case of older engines, the higher concentration of alcohol in the fuel acts as a solvent, even more-so that gasoline, getting rid of needed oil on both intake valves, and if there's any blow-by, from the cylinder walls as well. It will also play hell on any seals or lines not designed specifically for use with fuel that includes alcohol. Finally, being hydroscopic, it tends to attract water and cause rust.
Alcohol in fuel is a well known old engine killer. Sure, they can design engines to run on it, but it also requires more fuel for the same amount of driving.