As someone who was running tech at an e-commerce/hardware startup with $xxM+ in annual online sales, and ran on top of Magento 2, it is an unmitigated disaster that will sink any business that doesn't have endless money to throw at it.
We had great Magento developers working on it and could barely keep it stable under even moderate load. To scale up, if you're a heavily trafficked store, you need to pay a six figure annual license fee, or you can't shard/load balance your database. Without the Enterprise plan, your site can't easily do zero-downtime deploys, and deploys take about 30 minutes of full outages to get out the door. Editing anything took about 36 clicks, which carried the risk of corrupting a language you weren't editing. Deploying a language pack requires an outage. Deploying new CSS requires an outage. There were ways around this, which we used, but the extensions and ecosystem are so poor that I wouldn't encourage anyone to use them—we ran into one instance where installing an extension would bring the site to it's knees, at random, because the developer had hand-rolled an image-resizer for some reason to build thumbnails.
I'm an infrastructure engineer/developer originally, and I figure, how bad can it be? We'll ignore the snake oil and scale up with good developers and cloud hosting, along with best practices.
I can list how incredibly poorly built Magento 2 is for hours, but I've never seen anything like it. We made it work, but it cost us hundreds of thousands of dollars to get it to "doesn't break" level of stability.
It's outrageous particularly because the entire ecosystem is designed to shunt you toward expensive licensing that requires NDAs to be signed, certified developers to be used, and ever-escalatingly ridiculous hosting fees (at one point, I was quoted a $1500/month virtual machine to properly handle our environment).
Meanwhile, when we wanted to do a flash sale, Magento was so complicated and slow to deal with, we made the call to literally create a second store, using Shopify, to run our limited time sale. Not only did it take maybe 1-2 days to get it set up and working, we ran 1M in sales through it within the first 8 hours of it being online, without any outages, stability issues or anything else, without ever needing to do a payment gateway's time consuming PCI compliance security audit, either. We got paid out within a few days of even first signing up.
I think people underestimate, often, how expensive open source can be, and one red flag, in the case of Magento should be that anyone that isn't a "Magento developer" is terrified of touching it. (I have stories about how hard it is to even develop on your own machine, and how literally all roads lead to their Enterprise plan, with no way out, but that's for another day)