Why are there no skill trees?

[Felis]

Maybe if we can buy specific skills at the guilds with guildmarks again.
Of course at level 50 everyone with the same classs would have the same skills again because they bought every skill available.

Crossclass skills are also like skill tree. But we need more crossclass skills again. Maybe not all skills as crossclass skills like it was at the beginning from 1.0 (except the ones the players bought in the guilds), but more than we have now.