thank you for making the necessary effort in making the post.
since no one has responded yet, i'll just share 2 technical things you need to take note of.
1. When shooting an animal in full body, the placement of the head is very important.
The tiger's head in this picture is ''going out'' of the picture, and the angle of the face
showed little interest (one cannot see a ''readable face,'' and the animal turning away
also suggest a lack of interest.) A good time to capture an animal is when it makes a
direct eye contact with you or when it focuses on something else intently.
2. When shooting an animal in full body, the shape of the animal's image and the
juxtaposition of that image against the background is also important.
In your image, the tiger appears in an awkward shape. the viewer is unable to read the
expression of the body (tense, relaxed etc.) due to the distorted look. One is unsure
what the tiger is trying to do, neither are there clues to suggest what it is going to do
next.
Filling up the frame with the subject causes visual congestion, especially against an
uninteresting background. Congestion is not always bad, but it can be bad when you
are trying to simply feature your subject as object of focus. The left front leg of the
tiger ''hits'' the edge of the frame causing a lack of balance as well, showing the
indecisiveness in your framing.
Your friend might have said your picture looks flat because of the uninteresting light.
In this picture the grey stones do not provide any contrast for your subject to make
it visually more vivid as well.