I play strictly Vanilla, and solo as I have since the beginning. Far from impossible to play solo, it may be however impossible to bullheadedly face tank it all, in a mad rush to the end. This game draws a steep price on those who would attempt it. However, it is possible to play alone through preparation and timely measures to prepare the battlefield to your choosing. Picking where and when to fight, and when to leave, with your own pelt intact.
Knowing when you are outmatched and overwhelmed, is a crucial quality you will need to survive. Retreating with your life is a viable survival skill. But, it has no stat points. Good luck out there. Ask for advice? I have successfully acquired Iron, and begun stone-cutting without having ever engaged the Elder. I think I am doing fairly well solo, tyvm. I intend to capture an island containing a perfect mountain ring, and a trader inside it. All solo, all vanilla.