4th had major problems, at least with regards to retro.
The core box set was lacklustre, lots of miniatures but very samey and not very inspiring. Things got a little better with 5th, and improved markedly with every edition since.
The magic system requires expensive supplements which you either have got or have not. The magic cards were streamlined for 5th, making it less of an investment. Yes you could get magic cards for later editions but those were optional game aids.
Now I did like the ten spells per lore up to a point, the spells were colourful and varied, but as you only had 1-4 the ten spells lists became overly random.. Some of the spells from 4th did return in some form in Storm of Magic.