Does the play suggest that true love is possible and good?
It depends how you define "true love". If defined in the romantic sense, then this play does not represent that. Higgins and Eliza do not share romantic love. Eliza shows no desire for romantic love, but is more considered with her identity and her position in society. Likewise, Higgins is only concerned with intellectual pursuits, with being challenged and having new theories to test. The only character of the play that is associated with "love" is Freddie, whose desire for Eliza is not returned.
However, if true love is defined as the respect and friendship of another human, than this story could suggest true love is possible. Eliza and Higgins find a connection between each other, as do Higgins and Pickering. These three thrive off of their interactions. Although Higgins and Eliza misunderstand each other for a bit, they all respect each other. They appreciate the intellectual pursuits and small comforts provided by the friendships. This is why Eliza returns to Higgins at the end - she could take other paths in life, but she thrives off the relationship.