The Mesmer weapons aren't really that interesting enough to use on the other specs. Some examples:
The shield is a more of a tank, heal, support weapon. On chrono, makes a lot of sense. It fits nicely in its place as a chrono weapon. Chrono is a really good tank and shield really supports that. Mirage and Virt are both damage classes with no heal support so that's out.
Axe is a condi weapon. On Virt it doesn't make sense because condi Virt is based off of crit chance where you crit to apply bleeds You can really go all in bleeds and that makes a really good build. Axe may have some use here but its just not interesting enough. Chrono is probably the most interesting spot where axe might see play with axe but chrono in my opinion is more of a heal support class that does that role really badly. Chrono bit of a meme at this point. Would love to see some buffs to heal support chrono by the way.
Dagger is pretty decent. However, its not really all that game changing. The range is nice but im not excited to use the ambush skill on mirage and chrono, oh chrono.
Weapons mastery is a change indeed and it opens up more options to the players but its just weird. Cool on paper, but just kind of weird and not really all that exciting in game. This is Mesmer specific.