Shield was a % chance to block a shot
The % was a relationship between the strength of the shield, the max range of the weapon firing, and the current range to the target.
Eg. long range weapons were much more effective vs shields, short range weapons were often deflected. Rapid fire weapons were better against heavily shielded target as a percentage of shots would reliably get through.
This led to all sorts of relationships between units, and it meant battles were very dynamic - ships on FRD were always moving (usually one chasing another) in crazy patterns, and positioning really mattered (you could move a fleet close for mutually high damage battle or standoff at a distance where shots were less effective etc). Space tanks could only be harmed from absolutely point blank range, and Zenith Polarizers would turn heavily armored targets inside out with a single shot
The armor mechanic was introduced (I think) because this level of complexity was difficult for most players to understand and it made an already complicated game.. even more complicated. The armor mechanic (which admittedly I think doesn't work as well) made battles comparatively simple and static.
There were lots of things I liked about the old version, and I generally like to re-visit old games
