I would test the $replace() statements in Convert>Tag-Tag first
An when you have the correct syntax then use that template for the actions.
I think that you are sometimes missing the replace string, or the number of commas is not right.
Just thinking out loud but I wonder if perhaps the following could be a workaround in general for these scenarios:
Formatting the part of the tag that would be affected by the global action in a way that's reversible later in the action
Running the desired formatting on all the tags
Reverting the modifications in the tag you wanted 'excluded'
As an example of modifying the 'excluded' tag's content, using your square brackets replacement in the OP, you could perhaps replace all square brackets in the tag you wanted to 'exclude' with a special Unicode character you know won't be used for anything else, then at the end of the action replacing that Unicode character with the original square brackets.
Using your square brackets example, it was a workaround concept for excluding the action from affecting certain tags by changing the tags you want to exclude with different characters so the action doesn't affect them when run, saving the need to copy the replace action formatting for every tag you do want to change.
To visualize let's say the tag you wanted to exclude was Artist, but format all other tags with a square to round bracket replacement.
Original: Example Artist 
Formatting using Unicode replacement characters to exclude from later formatting action when run: Example Artist ⬔123⬕
Action that changes square brackets to round brackets is run and doesn't affect the Artist tag since the characters were replaced.
A replace format is run to turn the Unicode back to the original characters in the Artist tag: Example Artist 
Would be trickier for things like excluding certain types of capitalization however.
ohrenkino describes the functionality in another post back in December 2017.
The trick is to use an action of the type "Guess value" for the list of fields that you want to treat in one go and use a delimiter of your choice. Also, the bulk function has to be applied to the source.
An example: you want to remove the "The" from ALBUMARTIST and ARTIST:
Action: "Guess value"
Source: $replace('%albumartist%===%artist%,The ,)
Target Pattern: %albumartist%===%artist%
The === can be replaced by more or less any unique character.
I still haven't been able to make it work in my example though.
Found that wrapping the first %title%===%album%===%artist% within the replace function (as seen in ohrenkino's first reply to the topic) in single quotes formatted the fields instead as literal %title% etc.
You do not enter a replace string. You have supplied a data string, a search string but no string what to do with what the function found. It is simply a syntax error.
$REPLACE('%ALBUM% === %_DIRECTORY% === %_FILENAME%',' (ALBUM)',)
So, to break this down, we are instructing mp3tag to find album, directory and filename and within those tags any instances of ' (Album)'. Does it need another comma like in my example followed by '' to tell it to replace with that?
A:\Music\Record\INXS\Kick (Album)\1 Guns in the Sky.mp3
"Kick (Album)===Kick (Album)===1 Guns in the Sky"