Enter has been the command to enter rename mode for a long time. At least since System 7 in 1993.

That bothered me, too, when I switched to Mac, but after some years of use and renaming lots of files in Finder, I appreciate it over pressing F2.

You can also open any file in the Finder by pressing cmd-down (the apple key + the down arrow). It also works for folders, too. This is intuitive if you think about it this way: cmd-up navigates up one level in the hierarchy of your filesystem and cmd-down navigates deeper. If it’s a file, going deeper opens the file.