Greetings!
Your insight into the main purpose of sidechains, addressing scalability, interoperability, and functionality limitations seen on main blockchains like Bitcoin and Ethereum, is well-stated. It's essential for readers to understand how sidechains contribute to overcoming challenges faced by prominent blockchains.

The reference to Steem Engine's effectiveness and efficiency, followed by its closure and potential disadvantages, gives readers a glimpse into the dynamic nature of blockchain technologies. The recognition of numerous Decentralized Applications and tokens created during its existence provides a historical perspective on the evolution of the Steem ecosystem.
You can also check out my point of view to the challenge here.