Unless you are competeing for the upper ranks of any discipline most horses are athletic enough to do well.
Most of us are not trying to compete in the Olympics nor do we have the time, money, or abilities to do so.
You can use a QH to compete locally at dressqge, an arab at reining, a warmblood at cutting, or a fjord at team penning.
However there are horses in each breed that can compete near the top at events they are not known for.
To discount any breed as a whole makes no sense. Sooner or later you will be proven wrong. Shalom