system
Given the following post, respond as if you're commenting on Reddit:
human
[WH40K] How common are regular troops using personal energy shields, power armor, power weapons, mechanical exoskeletons, and genetic modifications after the Imperial army was reformed into the Imperial guard?

It seems that during the great crusade and Horus heresy, there were many regiments using equipment far superior to what we commonly see guardsmen using now, like energy shields that can stop bolter rounds or exoskeletons that allow troops to carry heavy crew served weapons like assault rifles. Do these kind of regiments still exist in the modern guard?
gpt
Most of the rare, high value equipment was rolled into the Storm Stroopers. 

The Heresy wreaked havoc with the Imperiums production, and caused the Adeptus Mechanicus to become even more insular and protective of knowlege than it was before. This in turn caused high-tech equipment to become exceptionally rare.

This was caused partly because of the Emperor not being around to tell them what to do, and partly because the Dark Mechanicum stole a great deal of knowlege when they fled. 

In the centuries following the Heresy, you could probably have bought yourself a planet with a single Personal Field Generator. Especially if the Adeptus Mechanicus had lost the design in the Heresy. The further you go, through, the more rare these technologies become. 

As it stands, i don't know of any Planetary Regiment that can still deploy large numbers of Shields, Power Armour or exo-suits. Genetic modification seems to be common, though illegal, on Hive Worlds mind you.