
SHORAD is not going to deny air attack capability for superior air force. It will make things more complicated and/or risky though. They force the aircraft to higher altitudes and keep longer distances to avoid being shot down. So enemy weapons have lower accuracy and effect or they need to use more expensive long range guided weapons. Of course nowadays such weapons have relatively low cost and are available in large numbers. Another point is that by forcing the enemy to higher altitudes, they become easier targets for long range SAMs and also fighter aircraft.
SHORAD systems have capabilties to shoot down bombs and cruise missiles, but they can pretty easily be overwhelmed by the superior air force. Basically aircraft can mass very quickly to one place and release a lot of munitions almost simultaneously. GBAD systems are fixed in place during operation and rely on overlapping to provide mutual coverage. Of course modern SHORAD systems can have fairly large number of missiles, so they don't run out as easily. Still a flight of 4 fighter aircraft can launch something like 24-32 SDBs, Spears or similar weapons. SHORAD might shoot down some of them, but likely not even the majority in most cases. And what happens when enemy masses say 20 fighters to launch 120-144 weapons at once?
It's always a game of cat and mouse. SHORAD systems are no wunderwaffe but they definitely have their own role in the battlefield. Especially if you can't rely on having much superior air force, then having decet SHORAD (and GBAD in general) defence can be very important. But alone they are not going to win any war. Combined with good fighter aircraft, longer range AD systems and early warning capabilties, they are much more capable.