There have been several disparaging remarks about the architectural merits the pools, both here and elsewhere. They were not listed when an application was made to English Heritage in 2006 but I though it might be useful, so that we can all be better informed, to give a couple of quotes from their advisor's report. His conclusion was that:
Forest Hill Baths is of interest as a surviving example of an 1880s covered public bath complex, which retains its pools and some other original features. They also make a positive contribution to the streetscape, and along with Holy Trinity School, Forest Hill Library and Louise House, form a distinct group of buildings which reflect the Victorians' enthusiasm for education and health reform. However, their architectural interest is limited in comparison to contemporary listed baths, and there have been significant losses and alterations to the interior. It is not of sufficient special architectural or historical interest in a national context [my bold] to fulfil the criteria for listing.
And the Countersigning Advisor added:
This baths building of 1885 has very strong local interest, particularly forming part of this ensemble of municipal buildings of similar date and materials. It also has claim to interest in the history of London baths provision. It is, however, a very plain building and while there are some concessions to design at the facade and with surviving interior features, there have also been significant alterations. Of considerable townscape and local history interest, but insufficiently special in the context of baths nationally [again, my bold] to list.
It is clear that they considered the pools to have significance in a local context (which is what we are concerned about); it was at a national level that the pools did not warrant listing.
Incidentally, the same architect's pools at Ladywell were recently listed gradeII.