Side-along Apparition probably requires more skill than just Apparating yourself.
The instructions for Apparition include “Let your yearning to enter it flood from your mind to every particle of your body.” This is probably easier if you only want to Apparate your body, rather than the body of other people too.
I believe we've seen only two wizards perform Side-along Apparition in the books. One was Professor Dumbledore, who has immense magical skill and experience. The other was Hermione, but she only used it as an emergency measure to escape from the Ministry, and then started regularly using it when they were fugitives and didn't have much choice.
Further, we know that Apparating can be dangerous. If someone without the experience tries side-along Apparition, there's probably an even higher chance of accidents than for just Apparating themselves, and they'd be risking to injure their passengers.
Dumbledore is dead by this point. Hermione might not trust herself enough to be able to perform Side-Along Apparition at this point, or the Order might not trust her to be able to do that, or they might not be aware of the full extent of Hermione's magical brilliance. If Side-Along Apparition is as difficult as I believe, then nobody else in the Order could perform it at this point.
(This answer is based on my previous answer "Why did Amos Diggory not use Side-Along Apparation?".)