You wish. Unless I'm terribly misinformed, "modern C++" contains all of the features of the prior versions, which means that in the real world you have to learn and deal with all of it.
Whether that feature is a good idea or not and to what degree, is the question.
The article is indeed still relevant.
You can write your code in modern c++ and ignore prehistoric carbuncles (some of which have been deprecated and eliminated FWIW). And you can call external code written in older dialects without having to look into its source code.
And if you're a Dirty Harry type like me, debugging issues with dozens of disparate codebases written in various crap subsets, you pretty much have to know the whole cursed thing.
Is there a list somewhere of features that have actually been removed from C++? (i.e., that would cause old code to break)
This is not what happens in the real world though.
While I agree that you have to deal with whatever is in your codebase at a given point, it also doesn't imply that you have to use everything and that everything can be useful for your project.
As standards keep coming and features get added, it's still increasingly prevalent to see guidelines and awareness around the topic of choosing your own subset of C++ to work with.
The main drawback is mostly that it incurs a cost in terms of brain power to discipline yourself to keep your work within a restricted set of language and standard library features.
It's extremely rare (and even debatable) whether a single person masters all the aspects and features of C++ (and if there's one, it's probably Alexandrescu).
Beyond that, even the "good" modern subset of C++ is crazy complex. I've sat in a room with some of the better C++ programmers in the world while they study and try to comprehend the new features like rabbis interpreting the Talmud.
If there's one concise, fundamental rule of software engineering, it's this: Complexity kills.
That makes as much sence as claiming that to develop software in, say, Python on the real world you have to learn and deal with all of its standard library.
That is not the case. That has never been the case ever for any programming language, be it large or small. Specially in C++, where since it's inception the standard approach is to, at best, adopt a subset of all features and stick with it.
I suspect this is not an uncommon situation among programmers.
So when you go to another project that made different decisions, what you should do is understand the decisions. It's quite easy. And that's why it's what people do do, and it's why people are capable of contributing to projects other than their first.
If you program in C++, it's the same skill you used to learn one or more of {CMake, Makefiles, scons, bash, python} except it's easier because you already understand the programming language's model.
"No true Scotsman" and all, please refrain from posting messages that add nothing of value besides petty insults thrown in broad brush strokes.
Picking up features in a language you already use is easier than learning the language to begin with which itself is easier than learning to program at all. If you were able to read the documentation to get to 50%, you have all the skills needed to pick up the rest and get to the difficult part of picking up a new project: understanding the problem space. If you're capable of learning the meaning of an API you've never seen before - and you will, if you're not writing your last project verbatim - then you're capable of learning what a lambda means. This is not me saying that all programmers should be able to do this, it's me saying that doing this is a predicate of engineering software.
You accused anyone who did not agreed with you of being incompetent and immature. In the very least own your own claims.