Most blog content is static, why would you need to use lambda for anything ? you already get automatic scaling by putting static files on S3. What Wordpress functionality would need to be implemented with Lambda ?
I run a static blog on S3 using Lambda. I upload a markdown post to an S3 bucket, Lambda runs Hugo (could be Jekyll, or whatever) to regenerate the appropriate files, then uploads it to an output buckets, invalidates the files it needs to in Cloudfront, etc.
Not infeasible to think you could use Lambda to generate a static cache of a WP site onto S3 and update files on demand.
It would provide unlimited and automatic scaling, simplified setup/architecture and we would pay only for what we use.