You know there's more to Odyssey than just on-foot combat? I also expect on-foot gameplay to expand even more in the future.
You're also missing out on tenuous atmosphere planets (you can see them from your ship but you cannot land on them in Horizons 4.0). So no driving about them in your SRV (on your spaceship game) or exobiology, or just enjoying the on-foot visuals.
Plus there's going to be some on-foot CGs coming in the future. Although there will be ship-based one's as well.
There is also much less to Odyssey as to Horizons 3.8 at the moment as well...
This is akin as to what happened a few years ago with the release of Egosoft's X-Rebirth VR version, the stand alone VR edition of the 'on screen version' where the dev team chose to remove or 'comment out' a lot of content of the 'onscreen' version because they assumed that it would drag FPS down on VR headsets. Nothing could have been farther from the truth.
A few modders made the 'recall' mod and brought back a lot of the content that was cut out (stations that were removed from the map etc...) and the mod got a lot of positive feedback.
Unfortunately, Elite Dangerous cannot be modded, and we cannot bring back the cloud and lighting effects, and the general atmosphere that we grew fond of in those 10 years of ED that led to Horizons, but which failed to materialize in Odyssey.
What I don't like about Odyssey, is that the devs made you grow fond of a lollypop with a certain taste for the last 10 years (let's call it vanilla for reference sake) and then rewrite the engine to include new content and new visuals but in the process change the taste to something completely different (let's call that strawberry for reference sake).
In short it's still a lollypop, it feels like a lollypop, and your tongue still recognises the lollypop shape, but the taste is completely off, it went from Vanilla to Strawberry without warning.
To understand what I mean: put your favorite VR gear on, fire up Horizons 3.8, play for an hour, then do the same with OD or with 4.0 and you will know exactly what I am talking about.
Like I said. 3.8 needs some TLC, but Odyssey needs much more than that. The reviews on steam from ODY don't lie neither and are also a far cry from what they are for Horizons.
ODY to me is a fleshed out Alpha, nothing more.