Python has the same problem though, as do "scripting" languages in general. The limit may be some low amount of "screens" as opposed to a literal screenful of text, but either way it's quite impossible to program "in the large" with it. Even Go is hampered in this domain by its limited abstractions.
What are other methods for slaying this complexity? And what are the languages that use it?
e.g.:
• Encapsulation. Keeping implementation details private is pointless when you deal with a small program (the implementation is right there on your screen), but it becomes valuable when otherwise it'd be too hard to check which details you can change and which you can't.
• Strong type systems. All the types are obvious when the program fits in your head, and seem like unnecessary boilerplate. However, when the program is large, it off-loads a bunch of sanity checks from your head to the compiler.
Same goes for design patterns. Writing an `AbstractWidget` and `WidgetFactory` when you have two widgets to deal with is overcomplicating. But when you have 50 widgets, you need something to avoid drowning in copypaste and spaghetti if/elses.
That's assuming you want scalability. If a language is absolutely never going to be used for scripting by beginners, it doesn't need to be used that way.
Newer languages like Rust, Swift and arguably Carbon don't make programming-in-the-large features "optional"; they make them as lean as possible, so that users can more easily apply them at the outset compared to older languages like Java/C#. That way even a screenful-length trivial script can potentially grow into a larger system without becoming unmaintainable in the process.
Let’s see…
Numbered lines as labels, GOTO everywhere. You got GOSUB if you were lucky.
All state propagated mostly via global variables. Subroutine parameters were present in dialects few and far between.
Now, variables. Maximum length of an identifier was what, 1? Or 2?
Inconsistent delimiters and syntax in general. Take GW-BASIC and its hot mess of graphical commands. Here you can’t have parentheses, but there you must. Semicolons here, commas there.
All the stuff that makes programs readable — consistent syntax, named procedures, reasonably long variable names, named labels if you must — all appeared very late, in QBASIC I think. But the rest of the BASIC world still had to cater to the lowest common denominator if your program was to be even mildly portable.
That aside, most of the limitations that you describe are applicable to BASIC as it was in 1970s (and some, like numeric-only labels and single-letter identifiers, are straight from the 60s). For example, GW-BASIC that you mention already had 40 significant characters in identifiers, WHILE loops, and single-expression user-defined functions.
I also don't recall anyone writing any serious amount of BASIC code while catering to the lowest common denominator for the sake of portability, simply because the dialects were different enough that it wasn't really feasible. Even on a single platform like DOS, going from e.g. Turbo BASIC to QBASIC required substantial changes.