Desktop or Web?

Question

Project management

Hello!
It so happened that I have experience in developing software for the Desktop (mainly in C ++ and Qt) and for the Web (PHP, Javascript). Under Desktop, I develop projects mainly for myself and for scientific research. Under the Web, I learned to develop so that I could periodically take freelance orders (Very rarely come across orders for the Desktop, which I gladly take if they correspond to my competencies).
Recently, a lecturer in the IT Project Management course was trying to convey a message to us. Let me rephrase as I understand it:

It is necessary to do projects under Web. Now it makes sense to develop for Desktop only specific projects. The web version is easier to make cross-platform, fix, update.

The teacher is the director of support and operation at the Center for Financial Technologies, a good specialist and a very cool man, so I didn’t argue with him =)
Suppose I want to become a Project Manager of a company developing corporate software. But I see the client part of corporate software as an application for Desktop.
Therefore, I have the following questions:

1. Is it true that it is better to develop software for the Web? Why exactly? Where can you read about it?
   
2. How to understand when you need to make a Desktop application, and when a Web application?
   
3. How is it less painful for a developer of Desktop applications to retrain for Web development? As a C++ developer, writing in PHP and Javascript is, to put it mildly, uncomfortable for me. Now I look towards C#.
   

I apologize for the large volume and some confusion in the wording of the question, it's just that this topic worries me a lot.
Thanks in advance.

Answer 1

First: Web Development != PHP.
Secondly: A competent project manager, he is an illiterate one, is distinguished by the ability to make a reasonable choice of technologies for each project, not on the advice of a teacher of some course (no matter how respected he is), but based on the specifics of the task (most importantly!) And (sometimes) on the availability /absence of developers with the appropriate qualifications or the presence / absence of the corresponding qualifications of the developers ( or developer a ).
Yes, there is a trend that desktop applications are gradually being replaced by web applications. And the reasons mainly lie in, I would say, the "inflexibility" of the dector developers. Having clung to any one technology (for example, .NET), they often forget that their client application is just a user interface to the business logic on the server. The task of the client is to be flexible, that is, not to depend on the environment in which the application is running. Web applications 100% satisfy this requirement, they work in any (modern) browser, under any OS, on any mobile / stationary platform and do not require any preliminary preparation of the environment (such as installing java, silverlight or adobe <their next platform>) . And that's the only way they win. For developers of truly cross-platform applications (including mobile platforms), not tied to any specific technology (especially proprietary) and undemanding to the execution environment, the threat from the coming web is minimal. They will coexist quietly next to web applications for a long time to come, and not a single manager will reproach the development team for choosing them.