We develop a large and very complex webapp with xojo, on which our entire company runs. So, developing very big webapps is absolutely possible in Xojo and I would always prefer it for ASP.NET (Core).
But you need to know some weaknesses of Xojo.
First and biggest is in my opinion the small userbase. It’s hard or impossible to find developer which even know Xojo (not speaking about that they are familiar with it). In the past we lost some good developer applicants which said, that they dont want to work in/with the xojo lang.
Next weakness is the performance. Xojo apps only run on one CPU-Core. So you may have some scaling issues if your App is used hard. We had many headache situation with the performance of xojo webapps. Just because they aren’t build for a high amount of parallel sessions/users.
Last is again the small userbase and the hard case around the technology. This forum is awesome and you’ll solve nearly every problem you’ll have together with the nice guys here. But it’s not the same as using stackoverflow with a more popular technology. It will happen that you’ll have an issue first and you can’t just search for a solution. This makes bug fixing or error solving much more frustrating sometimes. Also the webapp framework gives you not much possibilities to break out of it and make something different. You’ll alway need to stay in the high walls of the framework.
howsoever.
I’ve never regret the decision of choosing xojo, though. Because our development process is extremly fast and cheap compared to other technologies.
If the performance would be a big part in your project, I would rather recommend PHP or Node.js. The development is not as fast as in xojo and you have havily more work todo, but there are more developers out there which know both technologies and the scaling of thus apps will be much much easier.