+1 to this and your above points (the embedded team I'm on has started using C++ over the last year or so).
I've definitely learned a lot, and I like the portability of CMake for cross-platform use (our team uses all 3 of Windows, Mac, and Linux). My experience sounds much like yours: there've been a lot of times where using the vendor's flavor of Eclipse-based IDE (STM32CubeIDE, Renesas e2studio, etc) would have saved us a lot of discovered work, or extra work adapting the "happy path" to CMake and/or C++.
Using C++ and/or CMake is fine when it's part of the happy path and for simpler things e.g. STM32CubeMX-generated CMake project + simple usage of HAL. For more complex things like including MCUboot or SBSFU, etc, it's forced me to really dig in. Or even just including FreeRTOS/ThreadX, we've created abstractions like a Thread class on top -- sometimes it's nice and convenient, others it feels like unnecessary complexity, but maybe I'm just not used to C++ yet.
One clear, simple example is needing to figure out CMake and Ninja install. In an Eclipse-based IDE, you install the platform and everything Just Works(tm). I eventually landed on using scoop to install CMake and Ninja, which was an easy solution and didn't require editing my PATH, etc, but that wasn't the first thing I tried.
I have never seen any advantage of CMake over the much simpler GNU make.
Ninja is supposed to be faster for compiling very big software projects, but I have never seen an embedded software project that is well organized and which is not compiled in a few seconds on a powerful development computer with many cores, so I do not see the benefit of Ninja for such projects.
All Eclipse-based IDEs that I have ever seen are extremely slow for anything, both for editing and for building a project and they make the simplest project management operations extremely complicated. Even Visual Code Studio is much faster and more convenient than using Eclipse-based IDEs. Other solutions can be much faster.
While the example programs provided for STM32 MCUs are extremely useful for starting a project for them, I believe that using the methods of project building provided by the vendor results in a waste of time. I have always obtained better results and faster development by building a GNU toolchain (e.g. binutils,gcc,gdb, some libc) from scratch and by using universal GNU makefiles, which work for any CPU target and for any software project, with the customization of a few Make variables. I have written once a set of GNU Makefiles, according to its manual, around 1998, and I have never had to change them since then, regardless what platform I had as a target. For any new platform, there is just a small set of variables that must be changed by generating one per-platform included file, with things like the names of the compilers and other tools that must be invoked and their command-line options.
For new projects, there is one very small file that must be generated for each binary file that must be built, which must contain the type of the file (e.g. executable, static library, shared library) and a list with one or more directories where source files should be searched. No changes are needed when source files are created, deleted, moved or renamed, and dependencies are identified automatically. I am always astonished when I see how many totally unnecessary complications exist in the majority of the project building configurations that I have ever seen provided by the vendors or in most open-source projects.