Tales of Adventure

[Brightamethyst]

but for personal reasons I don’t intend to run any dungeons as part of a group.

Then you're playing the wrong game. EVERYTHING is locked behind some amount of party content. A story skill will only delay the inevitable. Eventually your options will be to join a party or quit the game. In Shadowbringers (level 71+) you can use trusts to run dungeons, but trials (8-man boss fights) cannot be run with trusts.

Out of curiosity, why play an MMO in the first place if you have such an aversion to joining parties?