Snapchat was founded in 2011 when people thought there couldn't be any other successful social media company. On the other hand, Salesforce, an epitome of SAAS, was founded in 1999. I believe there are always business opportunities and I'd argue there are more opportunities today because the space is more complicated and the cost of starting a company is much lower than before.
I don't necessarily disagree with your argument, but Snapchat might not be the best example. Snap has never posted a profit and their stock, even after a rise of almost 275% this calendar year, is still 42% below its IPO price.
