Steemit platform before the introduction of SEC, steemians only post in platform that they like and the interaction in the platform were specifically for those who have made a good bond with steemians.
Like you said people were free to migrate to any community of their choice and content were vote irrespective of the community.

The introduction of SEC have increased engagement in the platform, and you will have topic to write about everyday in order words it has increase our creativity on the steemit and boot our brain.
The content of steemians have increased in a very good way and they are higher chances of getting upvote from the chief curators again the moderators now have more work to do than before.

The introduction of SEC habe really had a positive impact in theige of every steemian as it has made us to more active in the platform and also engage with our fellow steemians.
Through SEC we now make new friends everyday on steemit.

I wish you the best 💯 mam in this challenge, do have a nice day 🤗