I would like to have a clear definition of 'secular Buddhism' as understood by the OP. I can make little sense of the phrase.
From the Wiki definition I can see no difference between 'secular' Buddhism and Mahayana. It seems to be a phrase used by those who believe Buddhism is about religious beliefs and the supernatural. As this is a wrong view the phrase seems redundant and meaningless.
I would normally assume that someone who calls themselves a secular Buddhist has almost no understanding of it.
As for Buddhism not being fit for today's world the idea is ridiculous. It's the same world it always was. I really cannot imagine how a modern human with internet access can confuse Buddhism with religious beliefs and dogma and oppose this to secularism. It tells us something about how little effort many people put into understanding philosophy and religion before leaping to conclusions.