Is there a simple way to practise fire worship more suited to modern times and not too complex and time-taking?
Rituals, code of conduct, etc were formulated to suit a particular region.They are not universal. You have the liberty to modify the rituals in a minor ways but can't change them in totality.
There is nothing known or called as Modern Priest. For example, in India having the most modern car doesnt allow you to drive on right side. Similarly you cant drive it on left side in U.S.A.
In south India, majority of men walk around bare chested, but the weather will permit them to do same in north during winter. So ritual is modified allowing them to wear clothes to keep them warm.
You stated - "practise the rituals on special occasions only." This is the most ridiculous statement I have come across. Remember you are either pregnant or not pregnant. You cant be half pregnant.
Read Rg Veda to understand how to pray to nature.