Wouldn't the same reasoning for BLOBs apply to JSON columns? Unless you're frequently querying for data within those columns (eg, filtering by one of the JSON fields), then you probably don't need to store all the JSON data in the DB. And even if that is the case, you could probably work out a schema where the JSON data is stored elsewhere and only the relevant fields are stored in the DB.
At the same time, I'm working with systems where we often store MBs of data in JSON columns and it's working fine so it's really up to you to make the tradeoff.
If you're only querying the JSON data and not returning it in full often, it's almost certainly fine. It's the cost of transit (and parsing/serialization) that's a problem.
At the same time, I'm working with systems where we often store MBs of data in JSON columns and it's working fine so it's really up to you to make the tradeoff.