I think it would be nice to add a little more variety in mountain height, and bring back large canyons with a little more frequency, etc.
But I don't agree with the "should have waited until confirming every planet was an upgrade on Horizons". I'm sure there's no way to avoid there being some boring, flat planets, short of making all planets ridiculously jagged and mountainous.
In fact, I want there to be some boring planets, to make finding beautiful ones rewarding. There were plenty of dull worlds in Horizons. Even with a re-roll that massively reduces their number (fingers crossed), I doubt there's any objective way to ensure the boring ones are always the same boring ones from Horizons.
So yeah, I think there's major room for improvement in Odyssey's planet geometry, but it's not something to be urgently rushed into (and potentially ballsed-up again), and furthermore it's not even the most pressing issue with the look of the planets. There's also the tiling surface textures seen from medium distances, the "Minecraft effect", the rate of asset popping/phantom shadows/invisible rock glitches, and the some big tweaks needed to the lighting system to give more visual contrast to surfaces (like we saw in the preview footage before release).
Those changes without geometry changes would have a groundbreaking (heh) impact on planetary visuals, IMO even greater than changing geometry alone.