Ant did not include IF THEN ELSE, unless you added the contrib package.
If you understood the paradigm, you could write branches in Ant files simply using properties and guards on properties ("unless"). Using IF in Ant was basically admission of not having understood Ant.
This said, I used Ant for a very limited amount of time.
As of Ant 1.9.1, you can use 'if' and 'unless' attributes on any task or element in a target. I stopped using Ant a long time ago, but this was a pleasant discovery when I had to pick up an old Ant based project recently.
I agree, that is what I meant: there were people who installed Contrib to have <if> element, but in reality you did not need that you could just use Ant's built-in features like you said. In my opinion installing Contrib to use <if> was a demonstration of not having understood how Ant works.
For new .NET SDK style projects you hardly ever need to customize the defaults and I know it's used for more stuff than .NET, but I just wanted to give an example where it actually doesn't suck. Also, you may not need to do everything in MSBuild, for some more complex stuff, you can use something like Cake (https://cakebuild.net/) in .NET for example and skip the programming in XML.
.NET made into my toolbox before it was announced to the world, thanks to be working at a MSFT partner that was selected to be part of the Portuguese launch event for .NET with ready made products.
Never seen any big corp using alternative .NET build tools, rather wrestling MSBuild, or before it came to be, nmake.
Ant came first, then when Microsoft redid the VS project format, they created MSBuild.
As incredible as it may sound, Ant is still easier to deal with than MSBuild.