It's not really "GUI programming" anymore. It's making HTML/CSS/DOM act like a GUI.
I've not been working on GUI programming much since, but I really enjoyed the Qt experience; good tools and superior documentation.
I never liked gtk - much for the same reasons as your Windows GUI C programming; Too verbose for trivial and mundane things.
Don't get me wrong, HTML browsers are fine for most documents and document navigation, but don't scale to real GUI's easily.
Not only have Software development not gotten any easier, most software are slo lots more resources intensive.
Nothing magic. Create it, set properties.
https://www.tmssoftware.com/site/tmswebcore.asp or
https://www.elevatesoft.com/products?category=ewb or
https://smartmobilestudio.com/
All three claim to be a form of "Delphi for the Web"
http://www.unigui.com/explore/what-is-unigui
https://www.atozed.com/intraweb/
This one seems to be also available for Lazarus ! http://www.raudus.com/
I wrote an old desktop app for medical laboratories in Delphi (started with D2 ...) and am still quite unsure if this would allow me to port at least some part of it for the web in an (cost and time ) efficient and secure way ...
Does anybody have some experience really using them ?
...Right?
https://anvil.works has a WYSIWYG visual designer, with Python for in-browser code as well as server-side. (We compile it to JS.) It's even got a built-in DB if you want it (Postgres-backed). Everything in one language, full front-to-back autocompletion...all the things we missed about Delphi!
The market has spent the last few years demonstrating that the sustainable number of large companies whose main product is open source is...One. (Red Hat, if you were wondering.) Even trying to become that kind of company requires a highly speculative VC-fuelled trajectory, which is famous for turning sustainable 100m-scale companies into 1% unicorns and 99% rubble.
Even Docker, which utterly transformed its target market, is barely making any revenue ($25m/year on a $1.3bn valuation). All its value is busily being subsumed into Kubernetes, itself a loss-leader from a company (Google) that makes all its money from something else.
Anvil-the-company is sustainable, profitable, and growing, and Anvil-the-product is getting better all the time, because we charge for what we produce. We would love to be able to give it away and keep doing that - but basically, we can't.
Ultimately unless there is an active and vibrant ecosystem, there is very little reason to consider your platform - especially when there are alternatives like Node.js, Django etc.
Also, for me I will be concerned about how I will integrate Anvil with third-party libraries needed for things like reporting, authentication/authorization, E-commerce etc.
Sure, the GUI wizard is not there for Django but what if someone were to develop such a wizard for Django? or what if someone were to say that it is best to stick with Django / Vaadin/Ketura/.NET/Go/Rocket.rs even if it takes another 25% more time to develop in because the ecosystem is much bigger and we can predict with more confidence that Django / Vaadin/Ketura/.NET/Go/Rocket.rs is going to be around?
HOWEVER, if your product was available open source, is a lot easier to setup and use than Django/Ketura/... (you could provide it as a docker image) and you had a business model where you provide hosting for that solution (similar to Heroku) and/or paid support, you may end up making more money because a lot more people would use your platform - lot more than your current model which very few companies will risk purchasing.
You have some nice looking tooling, but you insist on hosting the result and locking the user into paying rent to use something they built. Your on-prem is locked behind "if you have to ask you can't afford it".
You'd have more interest from people like me if I could just buy or subscribe to your tool and know that even if we eventually drop the subscription the application I produced would still be usable.
But I suspect that your goal isn't to convince people like me, but catch people reading this who might be more amenable to your terms.
Except the insanely fast compile times, native WYSIWYG editor, etc, etc.