@Halla I understand that with mod packs some more things would have been possible.
However many of the nesacsrily plugins can be difficult to work with mods.
Another advantage of vanilla is making it more accessible to players, without the need for a mod pack download, aswell as being able to keep the server constantly relevant.
We have been able to update to 1.9 already (and important combat update) due to being vanilla and not having to wait on mods, or worst case never updating due to a halt in pack development.