I noticed this too. I found the visual association lines really helpful for understanding how objects were connected, especially when learning HubSpot’s data model or explaining relationships to others. Without them, it’s harder to get a quick visual understanding of how everything fits together.
If this change was intentional, I would be interested to know the reasoning behind it. Personally, I would love to see the association lines return, even as an optional toggle.
In the meantime, one workaround I’ve found is to click the three dots on an object in the data model and choose View all associated objects. That will display the associations for that object, so you can still see how it’s connected to other objects,it just takes a few extra clicks compared to the previous experience.