From my point of view, it's still very valid to use campaign, especilly as a Customer Journey cannot be modified when it has been launched.
A CJ cannot replace a campaign (at least for the moment).
For ex, what we do on our side:
- We create Marketing forms, leads, marketing pages, etc... and we associate them to a campaign.
- We look at the campaign to have an overview of the lead generated from the froms
- We add manual activities like Linkedin paid ads, etc... to have an overview of the cost of the campaign.
P.