Coanda effect has relevance indeed ; it effect shows in its purest form the Newton law, thanks to
which the lift is generated. In fact , even without any pressure difference between upper/lower side, the curved shape generates lift,
thanks to imparting a deviation to the fluid flow - try with a spoon under tap water flow, where pressure is the same
on the upper and lower side of the spoon (it is the athmospheric pressure, both for the water side and the air side ) .
Obviously , for Coanda effect to take place, fluid shall not be inviscid,
otherwise it will not remain attached to the "upper" side, and consequently will not be forced to deviate from its initial direction.
When I tought basic aerodynamic to pilots, I started with water skis ; there, the lift is generated purely by deviating
a mass of water, creating an opposite force which lifted the ski. Independently from the difference in static pressure above and below the ski
(which is nil, since above the ski there is the static sea level atmospheric pressure , and below there is the static sea level water pressure,
which is equal to the atmospheric pressure !), lift is created just by deviating, the incoming water flow, which obviously creates a dynamic pressure.
The beauty of the wing profile is that , thanks to specific pressure distributions obtaine throug a peculiar shape, it is able to deviate the incoming mass flow with much less drag
than a water ski, even at a zero angle of attack, wsomething that the water ski is not able to do.