Types 22/23 are not Anti Air; they're ASW and AS. We've already spent the money getting the best AAW DD. Every additional one we now buy is, arguably, saving us money.
Agreed the T23 is an ASW platform and the T22/III was the most capable platform we had. Both need replacing and either a variant of The Type 45 or a variant of the AD destroyer re equipped as an ASW platform or GP frigate would be a good idea.