Sorry, I am not saying they are very bad. Just saying "relatively" unsuitable.
[What I understand]
Adding CAPTAS-4 (or CAPTAS-4CI (has shorter tail)) will make any ship "so-so good at ASW". "To what extent", I understand there is no open information.
- There are many MEKO200 class. MEKO200 of RAN and RNZN has a (relatively) small hull sonar "spherion-B" mounted, and they say it can do ASW.
- Dutch M-class frigate are known to be much better ASW ship (compared to MEKO200). They have CODAG propulsion with rafted diesel, but they are specifically designed for ASW in "passive TASS era", with "good" hull-quiet-measure in mind. When adding LFAPS active low-frequency VDS+TASS system, they saw "quantum leap" in ASW capability. (I remember there was a report saying that Dutch navy omitted passive-only mode from their low-frequency VDS+TASS system. Interesting)
- French FDI (with CODAD propulsion and CAPTAS-4CI sonar) is designed under the policy that "not-so-quiet but cheaper hull combined with CAPTAS-4CI" in larger number. It is an alternative to FREMM, which has CODLAG propulsion and full-fat CAPTAS-4 sonar suit.
- T23 overwhelms M-class frigate (not to say MEKO200) in its ASW capability, investing a lot on hull-quiet-measure, with CODLAG propulsion. But of course, M-class frigate with "active low-frequency VDS+TASS system" will be much better in ASW capability than T23GP (without CAPTAS-4)
None of these "ASW doable" frigate has side-thruster. None. In all ASW-related textbooks, it is said that "omitting side-thruster" is important for ASW. USN FFG-7 class has retractable azimuth thruster (which was also the 2ndary propulsion, as she is a single-shaft escort) has a so-so good cover on the azimuth thruster to reduce flow noise.
[What I guess]
An IH-class with CAPTAS-4 or CAPTAS-4CI will do ASW much better than even a T23GP. "Active low-frequency VDS+TASS system" is a game changer. But, I guess "M-class with CAPTAS-4CI added", "MEKO200 with CAPTAS-4CI added" and "FDI with CAPTAS-4CI added" will be much better than "IH-class with CAPTAS-4CI added". This is my point.