Nowadays it is very very closed. Read the “Gebruikersvoorwaarden” and you see it is far from open.
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old.observation.org is not that bad but i always use the app, not the website.
The new website is up to date with userinterface but works 3 times slower.
Anyway, now I’m torn again, it would be a lot of work adding a few 100 observations to a slow and buggy website (makes me realize how spoiled I am by inaturalist), but it does seem to be used a lot