Samurai
Adventurer
One of the things I've liked about 5e is the ability to have the same theme over multiple classes. This is done in 2 ways: backgrounds and archetypes.
For example, let's say you wanted to play a sneaky, Thieves Guild type of game. Not everyone has to play a Rogue, you could have characters take the Criminal background, and/or choose sneaky/trickster type archetypes. You could have an Illusionist Wizard, a Way of Shadow Monk, a Fey or Great Old One Warlock, and a Cleric with the Trickster domain.
Do you want everyone to be students at a magical school? Many classes have a magical option now, like Arcane Trickster and Eldritch Knight.
Most any theme now has multiple choices to it, such that there's no need to ask "Is it viable to have an all-Rogues party?" The answer is yes because your roguish party can now have a tricky wizard, cleric, and other classes just like any other party, and they'll all be able to contribute to the theme in their own ways.
For example, let's say you wanted to play a sneaky, Thieves Guild type of game. Not everyone has to play a Rogue, you could have characters take the Criminal background, and/or choose sneaky/trickster type archetypes. You could have an Illusionist Wizard, a Way of Shadow Monk, a Fey or Great Old One Warlock, and a Cleric with the Trickster domain.
Do you want everyone to be students at a magical school? Many classes have a magical option now, like Arcane Trickster and Eldritch Knight.
Most any theme now has multiple choices to it, such that there's no need to ask "Is it viable to have an all-Rogues party?" The answer is yes because your roguish party can now have a tricky wizard, cleric, and other classes just like any other party, and they'll all be able to contribute to the theme in their own ways.