Isn't this a great opportunity to sell us on your solution, or get our feedback? You don't need to reveal details of your approach, but what are the actual problems you see?

As a company that has built our most recent site completely on serverless, we've become familiar with some of the issues. Though I definitely would not consider it a no-go.

That sounds like a very pertinent thing to disclose when offering a critique of a competitor, particularly when you're not able to substantiate (for legitimate reason or otherwise)

Sounds even more fishy

In that case you might wanna take another look at the answers here. Notice how they all use Amazon Lambda?

If you intend to compete with them - you might wanna reconsider.