It's possible to see a lot of Scotland by train and bus (I spent 26 days there without a car last year), but you will be limited in where you can go and how much ground you can cover if you also want to avoid tours.

Yes, you can absolutely enjoy a fulfilling and scenic trip to Scotland without a car, as the country has a robust public transportation network. Major cities like Edinburgh and Glasgow are incredibly walkable and linked by frequent, fast trains that take only about 50 minutes. For the Highlands, the West Highland Line is widely considered one of the most beautiful train journeys in the world, taking you from Glasgow to Mallaig and crossing the famous Glenfinnan Viaduct. Furthermore, the "Citylink" and "Stagecoach" bus networks reach many rural villages and trailheads that trains do not. For the islands, Caledonian MacBrayne (CalMac) operates an extensive ferry system that is easily accessible as a foot passenger. Many travelers also utilize small-group tour operators (like Rabbie’s) which provide guided transportation to remote locations like the Isle of Skye or Loch Ness without the stress of driving on narrow, winding "single-track" roads. By using a combination of the "ScotRail" Spirit of Scotland Travelpass and local buses, you can see the vast majority of the country's historic castles, distilleries, and lochs while enjoying the landscape through a window rather than focusing on the road.