"Why do I need to worry about small language specifics like brackets, terminators and so on when tools should be able to auto-complete them for me?"

Actually, if you are using an IDE, there's probably a flag you can flip for that. It's a very common feature, to the point that I often find it in places I'm not expecting, like the web-based security training code platform my employer periodically pushes us through.

I'm not a fan, but some of it is just that my habits haven't developed around it.

There have been a number of tries at going even deeper, and trying to make it so the code is valid at all times. I suspect this one fails because we pass through more invalid states than people realize. For instance it's not uncommon for me to copy & paste some data from somewhere to embed into a program, and to massage it in my code editor until it is valid syntax, but it isn't "valid" until the very end. Smaller scale things like this happen all the time. It is more constricting than I think people generally realize to have to be valid every second.

"You're editing a file (or parts of different files) and are focusing on say 5 methods that are interacting. I want to see all of them on the screen at the same time, without having to struggle to open and manage many windows with for example VS horizontal/vertical sliders."

We've tried that already... and actually I'm with you, it's awesome. I suspect this is just because by the time you've got all the other IDE gizmos on the screen it's hard to do too much splitting. But my normal code setup is three emacs windows side-by-side on the screen (and, that is, windows, managed by the windowing system, not "frames" within emacs), each of which then can and often are further split once vertically. If I have to go all the way up to truly using 6 contexts at a time, something has probably gone wrong architecturally, but 2 is extremely common and bursts up to 3 and 4 a daily occurrence.

Watching some people recently trying to get into a largish code base, and watching them interact with it basically through a single window and at times not even with an IDE, really makes me think one of the larger problems is people learning how to "turn the lights on" in a code base. It isn't even a matter of implementing features at this point, honestly almost any environment already has a ton. You need to learn to use them.

"Data conversion. So I created a HashSet for something but realize I need to change it to a Dictionary or a Tuple, just make it happen."

We tried that already... and it comes with some substantial costs you may not realize.

First there's the obvious performance one. Make it easy to auto-convert them back and forth without any syntax fuss and you'll end up people writing loops in which the 1,000,000-million element hash table is converted both back and forth between a hash table and a tuple list in a loop, once per element, and you end up with the sort of bloated programs we all like to complain about. (Indeed, this sort of thing is one of the root causes, though far from the only one.)

The more subtle one is that automatic coercion, of which this is an example, is just generally a bad idea. The programmer ends up with a too-fuzzy idea of what is going on, and that fuzziness manifests not just in the aforementioned performance issue, but also, bugs, when it turns out that the properties of various structures being autoconverted back and forth are actually important to the code. The most common example which is increasingly widely regarded as a bad idea is "falsiness", where the language tries really hard to have a concept of true or false for all sorts of data structures, but the bugs that emerge from empty strings being read as false unexpectedly and such make this generally not worth it. In the case you cite, the data structures are not the same; they differ substantially in what they do with multiple values for a given key, and how order-sensitive they are, and in the world of programming, these details all matter. Especially because they end up being used to construct security systems.

It is hard to see the general sweep of programming language development, but in general at the moment I think languages are headed away from auto-conversion. What you can see is languages and libraries developing better "interface"-like abilities, where maybe they can declare that they just need this or that bit, and then you can pass multiple different structures in. See for instance __getitem__ in Python. This is a much better approach; there's still some fuzziness cost but the offsetting benefits are much stronger so it's a much better trade.