What is your guess, how much the team budget would change for these "R5+" cars? Let's say the yearly budget is now 100 million euros, how much of that would be reduced with cheaper cars? And how expensive would these "R5+" cars soon be if the manufacturer teams could start tossing money into them with the intention of winning the title (not making profit by selling cars to privateers)
Now, think again: could it be possible that there's currently only two manufacturers in the world who are interested in putting any money in supporting a whole WRC team, regardless of the car type?