I don't understand the supposed issues with Google Photos captions. Embedding the caption in the jpg photo file is the logical place for captions since it stays with the photo wherever it resides as opposed to external captions that don't follow the photo. If you were a Google Picasa user before the Google migration to Google Photos, the captions were still there.
Obviously I agree with the belief that Google Photos currently is as good as or better than any of the alternatives for all aspects of photo management as suggested in previous posts. Who knows if this will remain true as technology evolves but I am quite happy with Google Photos today and it keeps getting better.