I've worked on many Drupal sites, and I would say the sweet spot is a client who is going to budget $10k+.
Basically, under $10k budget means you should be looking at simpler, pre-baked solutions, like Wordpress, Squarespace, Shopify, Wix, static HTML, etc..
I've worked on Drupal projects from $25-250k+, and it can handle pretty much everything (sometimes requiring a lot of TLC tho).
There are so many contributed modules that can help build things out, but I always need some type of customizations requiring (usually a few) custom modules per project. It all depends... I did one project that had dozens of crazy features that we broke out into 70+ custom modules...
But yea, I would say the sweet spot is a customer who needs a pretty large site with a lot of functionality. My 2 cents anyway.
There are so many contributed modules that can help build things out, but I always need some type of customizations requiring (usually a few) custom modules per project. It all depends... I did one project that had dozens of crazy features that we broke out into 70+ custom modules...
But yea, I would say the sweet spot is a customer who needs a pretty large site with a lot of functionality. My 2 cents anyway.