Is it? What functionality are you thinking about that absolutely require more than that?
I find that most ideas even today can be solved with a web server + DB, while developers today like to over-engineer things and think about scaling a service for a million users while they haven't even figured out the value proposition of their product/service yet.
A lot of apps use an "AI" or "machine learning" component which usually just means a second heterogeneous internal service.
For a little bit larger companies it's pretty common to have a data analytics or data warehouse component.
In addition, a web server + database usually require some monitoring system. After you have more than a handful of servers, probably also log aggregation.
If you're just a single or handful of people working on something, you probably don't need any of that.
Once you get a little bigger (or downtime becomes expensive) those things get tacked on quickly.