I believe the OP is talking about
Live Horizons, not Legacy Horizons. Your comment doesn't apply.
To de-confuse things:
- "Legacy Horizons" is the old version of the game (version 3.8, which you can see on the bottom left of the game's main menu), which is the one available for consoles (and for PC if you want to download it). It can still be played but development was completely discontinued years ago, and its universe is completely separate from the current Live version. There's pretty much nothing happening there.
- "Live Horizons" is the current most up-to-date version of the game (version 4.x on the bottom left of the game's main menu), but without the Odyssey expansion.
- "Odyssey" is Live Horizons + the Odyssey expansion. This expansion has to be bought separately.
What the OP is most probably talking about is the Live Horizons version, without the Odyssey expansion.
To be clear: They are the same game (same engine, same content, same shared universe, same events, everything the same), except that some Odyssey content is unavailable if you are playing in Horizons mode. This includes on-foot content, exobiology, ability to land on thin-atmosphered planets, certain engineers, certain materials, certain odyssey-only surface ports, and nowadays any of the new ships.
To the OP: Yes, that means that you are not merely missing being able to disembark your ship. In Horizons you can't land on thin-atmosphered planets, while in Odyssey you can. Likewise exobiology (which is highly lucrative) is not possible. Also the new ships are Odyssey-exclusive.
To get a taste of what you are missing out when you can't land on thin-atmosphered planets, here are a couple of examples:
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