You need to always ensure Z=0, for Text, Mtext, Attributes in block and more, or you will always get the 'fuzzies'. THis is done by controlling your cursor's Z elevation, ensureing any objects you snap to are also at Z=0 and more.
If you can't get Flatten to work, the simplest oldest macro below will fix them all too, put it in a button:
Or LISP the macro if you are a typing cadder:
(defun C:FLAT ()
(command "_.move" "_all" "" '(0 0 1e99) ""
"_.move" "_p" "" '(0 0 -1e99) "")
Or at the commandline you can try:
0'-0" (or plane elev)
Never forget that AutoCAD is a 3D program.
If you prefer broken-pencil-drawn text, there is nothing wrong with old-school SHX fonts, they still work.