I was similarly underwhelmed by the Fortitude so here is what I did with it.
I made a triple batch of the Fortitude, starting in June '16. By May '17 it was about as good as it was going to get and ready to bottle but I did not like it so I left it in 3 each 5 gallon carboys for more than a year.
I was making a "Super Tuscan" of my own design using two California juices, 12 gallons of Cabernet Sauvignon/Merlot blend and 6 gallons of Sangiovese. This was started in September '17 and I had added a 96 oz. can of Blackberries and a 3 lb. can of Blackberry puree to primary. It was okay after about a year, but not spectacular. I had also made a 3 gallon batch of blackberry wine about a year earlier and it was aging well, tasted great but a little on the thin side.
By June '18 I had three wines which, while each had some great attributes, none was outstanding on its own. I decided to do some blending so I created a wine which I call "Debutante" (after my daughter) which is 50% Super Tuscan, 41.7% Fortitude and 8.3% Blackberry. I put this all in two demijohns plus a 6 gallon carboy, with oak, currants and raisins and let it age for more than a year. In August '19 I bottled 160 bottles of the new wine which had turned out great.
It was a long road which I would not want to travel again but worked out well.