I am not sure I am missing the point. As you say it is a level playing field if you have a MarkIV. Implying that if you don’t it is not.
The point you are missing is that as Colin suggests it was never a level playing field with various Mks and especially certain wooden boats always winning in certain conditions. While I am happy to give credit to some good sailors I do not believe that their sailing ability was the sole factor in their success. On that basis and with new comparable wooden boats being unobtainable the class was dying. Atempts by a couple of Irish boats to bring competitive wooden boats into the fleet highlighted the problem especially ensuring conformity of the hull shape.
The MkIV has made one level playing field leaving many good secondhand boats for others to learn to race and buy a MkIV when they feel they are good enough as a sailor that only the boat now will make a major difference.
I voted against the Mk IV but I now realise that I was wrong and the MkIV is the best thing to re-invigorate the class.
Spending money, for most of us, is a balance of priorities but pleasure for £ I believe dinghy racing and the versitile Wayfarer is one of the cheapest pleasures. Remember that the final cost is only the difference between purchase and final selling price.