It is true that Sheets isn't as powerful as Excel. But it's a good substitute for 99% of users. And for people dealing with complex models/large amount of data, they should probably use a proper programming language (Python, R) and version control.
Google Sheet's limit of 400k cells sounds like a lot, that could be as few as 40k rows with 10 columns (probably lot of them would be dimensional). As someone who works with large amounts of data and business users, it sounds nice to say everyone should learn to code and query, but in practice the business users can get a lot done with a big spreadsheet with fewer errors and less training. I frequently hold classes to teach SQL, and even that is pretty tough for a lot of people to learn and do correctly.
It’s 2m cells, not 400k.
Have you ever heard of LibreOffice Calc, which from my experience greatly outperforms Excel?