I am fairly successful with most fruit trees in my yard (around 55) but there are some chronic underperformers.
Mangos: Keitt, Lemon Zest (severe MBBS problems). Didn't meet expectation and were removed.
Dragon fruit: Purple Haze, 1 fruit in 10 years. Didn't meet expectations and had to go.
Lychee: Sweet Heart: problem with weevil and LEM, light producer. Brewster and Mauritius are much more resilient and produce 10x as much.
Mamey: Viejo; 5 years and so far not a single fruit. Does it need a 2nd Mamey near by?
Acovados: Oro Negro, keeps on dying back. Tried a 2nd tree in same spot, same problem. Now planted a Sapodilla that performs fine. So I don't think it is the spot.
Lula, tree grows OK (3.5" diameter, 8' tall, healthy looking leaves), but not a single flower in 5 years. Bacon, Monroe and Brogdon all perform fine.
In paricular the Mamey, Sweet Heart and the Lula Avocado are poor performers. Is it time to move on and plant something else?