Not merely the ide, but the compiler/linker/debugger which are the more
important bits undelying the toolchain IDE.
These toolchains come with either artificial crippleware features  (code
limit, seat limit, missing usb/network/filesystem libs) and /or huge costs.
Further they invaraobly involve a hefty charge when you migrate to a
fifferent processor family. Not to mention en passant that most of them are
windows based.

Even more irritating is that many of them use freesoftware (eclipse, gcc,
gdb etc). And, if one looks hard enough, you will find the linker and make
scripts, usually in a horrendous messy maze of directories. NONE come with
any code management tools.

Not to mention the idiocy of clicking 20 buttons in an ide when a simple
script will do all of it and a lot more.

*If it doesn't support GNU/Linux tools then burning a hex file will*

Very big. Many dev system + board  makers + micon vendors are involved in a
dirty game that deliberately does not publish the programming and debug
interface specs / algos. Which requires you to buy costly, unmaintainable
programmers.
Eg SWD interface. Latest news is that the specs is being opened up to the
openocd devs.

While gcc and friends have a huge panoply of features, they also have a
learning curve. The plus side is you will learn a lot more about your
targets and you need learn it only once and it will last you forever.