More than 90% for web business will continue to make money. We are a team of 4 people company and we use 15+ SaaS Web tools and we can code few of them but we see no reason to solve. Why would we replace Calendly already at just $12 per month? Or why would we will create an internal Outlook?
SaaS was always about the service part and works better when other companies use the same tool.
Unique software specific to business needs will get more interesting though.