I enjoy both contemporary games and OSR titles, for different reasons. I can appreciate the crunch of PF2 or even (gasp) 4E. OSR gaming is more about kicking back, beer and pretzels, playing with friends. The robust tactical approach helps satisfy my desire for wargaming.
That said, if I were playing a solo adventure, I would probably go with a more modern, rules crunchy system or solo dungeon crawling board game with AI controlling the monsters.
There are some good YouTube videos about people running solo games using random charts and AI for monsters. One that seemed to review highly was Forbidden Lands, but you could probably take the principles and apply to any system.
That said, if I were playing a solo adventure, I would probably go with a more modern, rules crunchy system or solo dungeon crawling board game with AI controlling the monsters.
There are some good YouTube videos about people running solo games using random charts and AI for monsters. One that seemed to review highly was Forbidden Lands, but you could probably take the principles and apply to any system.