What you're looking for is called a Walking Simulator—no explicit goals or win state. There's a nice niche for them in games like Proteus. I wrote one myself in 2007, before the genre had a name. You are a single pixel just exploring an ultra lo-fi pixel land, to see what you can discover: https://doomlaser.itch.io/standardbits
Sort of. I played Proteus a little bit and it was definitely along the right lines, though I wouldn't say the genre as a whole is exactly what I mean. Many walking simulators like Dear Esther and Gone Home are pretty linear, where "exploration" mostly means unpacking a specific story in the exact order the developers planned. Some others, like Eidolon, still can't resist putting little collectibles in there.
Maybe there should be a genre distinction for truly "walk in the park" or "hike in the woods" style experiences, though even in the woods or at a park you'll often encounter trails or paths, which tend to shape a more linear experience.
There are plenty more on itchio as well: https://itch.io/games/tag-walking-simulator