The UI is a convoluted, ugly mess of different looking interfaces, popups that lock you out of the main window of the software until you press cancel or ok. Many things are in completely different areas multiple times. A shitton of tools don't even have icons.
I don't like icons. I guess it is preference.
It's slow as hell. The bootup, even without plugins, takes ages. After it's opened up it freezes for a couple of seconds until you're able to use it. Even in simple scenes, many tools and windows take multiple seconds to even open up.
you may check your workstation. I have tons of plugin. It took about 40s. There are some tools takes 1-2 sec to open. But, mostly It opens quick here.
There is almost zero feedback on what tool you have active or what is actually happening at any given moment. I've lost count on how many times I didn't know which tool I have active, forcing me to use it, just to undo and select the correct tool.
I'm not sure why you need to know what tool you have active. Modify panel shows what you selected. It also indicate if you are in sub-object or not.
It's buggy as hell. Freezes and crashes constantly. I've used 2018 and 2020 so far. Both seem to be equally bad.
Again check your hw. I rarely got crash with millions of polys.
You cannot do simple calculations inside any of the numerical fields. If you, for example, try to move your object 20cm up you can't just enter "+20cm" at the end of the Y (in Max Z) coordinate. Nope, gotta calculate that in your head or with a calculator and then copy paste it. Have fun calculating "2.175 * 4" instead of just entering "*4" and pressing enter.
CTRL+N
Many of the tools I've used so far are more or less destructive in nature.
Not sure why it is destructive.
The material editor is horrible. Every single material in the scene shares the same node window. You can manually open up more tabs, but why would I ever need ALL my materials in the same window?
Why you need ALL material in a tab? As you said, you can put in each tab if you want.
The "object manager" (I don't know what it's called in Max) is probably my biggest gripe. It's pretty much unusable outside of specific circumstances. This is probably my biggest issue since I'm so used to doing everything with the object manager in C4D. It seems like you have no overview of what the scene contains or how it's built.
When you use Max you mostlyl manage scene with layer. I'm not sure what is issue here.