Indeed, Unity's main problem is that its core weighs ~3MB and we can't do without it. But for a professional use, where the user can afford to wait a few secon

Indeed, Unity's main problem is that its core weighs ~3MB and we can't do without it. But for a professional use, where the user can afford to wait a few seconds for the loading, it seems to me suitable. It's possible to cache the core so that it won't need to be reloaded in the future. WebGL export is officially not supported on mobile (even if unity supports touch screens), but in fact, when you know what doesn't work on mobile (some shaders and textures), you have to be careful. The big advantage of Unity is the speed of development, the huge community, tons of free resources, an active forum and very powerful features. I don't know enough about other engine, so I cannot help you for choosing