That's a tad harsh.
The SHar has a useful AD capability, and an excellent little radar, though it is restricted by:
1) Several factors which cannot be overcome
Modest payload
Very modest range/endurance
Lack of supersonic acceleration
2) Some factors which could be overcome with relatively modest spending
Lack of ASRAAM/HMS
No longer routinely carries a gun
The real problem is that the RN's carriers aren't big enough to carry a meaningful number of SHars if GR.Mk 7s are also embarked. They can function as AD ships with SHars and Sea Kings, or as power projection ships with GR.Mk 7s, but if a mixed complement of GR7s and SHars are carried there are insufficient of either type to do the job.
The decision has been taken that the Fleet AD role can be 'done without' for the nine or ten years until JSF arrives, leaving a capability gap which will have to be covered by land based AD assets or by our allies. It is recognised that in the unlikely event that we had to do a unilateral autonomous Falklands type op (a most unlikely circumstance) we would be f*cked, but that if we retain Shar we would have to do without more useful capabilities.
The reasoning behind the decision was the sensible but still contentious belief that the carriers would be more useful if they were to embark an all-GR7 air wing.
It could be argued that the Shar should have been retained in order to give us the flexibility to use the carriers in either role, or even with a mixed complement if we accept the gaps in AD cover that would result. On the other hand, retiring the SHar will provide significant savings (including the cost of some vital but expensive upgrades), and will solve the developing manning crisis which was starting to emerge.
If a fast jet type had to be withdrawn prematurely, then the Sea Harrier was the least painful cut to endure.