I'll add that some people buy a horse FOR a sport, and others (me) buy a horse and then look for a sport.
For the first person, suitable means "a good horse to buy in support of my chosen sport". For the second, suitable means, "good enough".
My little mustang is good for my purposes. However, some of the things that make him a good match for me would make him a poor choice for jumping. He has a heavy body for his size, and thick legs. He was born wild, and is cautious about his footing. For an adult male riding in the desert, he does fine. The solid body and legs can carry my weight. When picking the way thru rocks, his caution keeps us safe. Safe is very important to both of us!
Although he can jump, his build works against him. Heavy weight for his height means he'll never say:
"I have slipped the surly bonds of earth
And danced the skies on laughter-silvered wings;
Sunward I've climbed, and joined the tumbling mirth
Of sun-split clouds..."
Indeed, he has no desire to dance the skies. He wants his feet on the ground. Think Gimli!
In the future, one of my granddaughters may want to learn jumping, and he could do it - at a very low level. Beyond that, he would not be suitable.
Gratuitous Internet airplane pic - humor a former WSO/EWO who would gladly "slip the surly bonds of earth". It has been a long time since I had a chance to play with the clouds