Passage
who once was to thee unprofitable, and now is profitable to me and to thee,
who once was to thee unprofitable, and now is profitable to me and to thee,
Philemon 1:9 because of the love I rather entreat, being such an one as Paul the aged, and now also a prisoner of Jesus Christ;
Philemon 1:10 I entreat thee concerning my child--whom I did beget in my bonds--Onesimus,
Philemon 1:11 who once was to thee unprofitable, and now is profitable to me and to thee,
Philemon 1:12 whom I did send again, and thou him (that is, my own bowels) receive,
Philemon 1:13 whom I did wish to retain to myself, that in thy behalf he might minister to me in the bonds of the good news,
The verse centers on "once", "thee", and "unprofitable". It is saying that the verse draws attention to "once" and "thee", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 10's "I entreat thee concerning my child--whom I..." into verse 12's "whom I did send again and thou...", so "once" and "thee" belong inside that flow. In Philemon context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "once" and "thee" with trust shaped by these words, not by a vague optimism outside the passage.