I've been going to Concordia for years and through several different ownerships. It certainly isn't the Concordia of old, when it was owned by Stanley Selengut and before Hurricane Irma, but it's probably the most affordable accommodations on the islands with the best views.
The tent cottages, which they are now calling Cabanas for some reason, are rustic but really all you need in this climate. They could do a better job equipping them with amenities. Pots, pans, dishes, and utensils are a hodgepodge.
The office was closed the entire time we were there, 2 weeks. The volunteers were really the face of the place, and they were great. The restaurant was open every day, as advertised, and the chef, Bernardo, was fantastic. The power went out several times during the week, which was not Concordia's fault. One evening when the power was out, Bernardo and Maya (the volunteer) continued to serve dinner and did an excellent job.
Hannah, the host, was great and very responsive, even though she wasn't on-site.
What the resort lacks, which it had before, is a sense of community and engagement. If they could cultivate a core on-site staff presence (i.e., office staff), it would make a huge difference.
Nonetheless, I will continue to go back and do recommend it.