That’s not a great business to run though as it’s very difficult to scale.
Far too many fall into the trap of saying yes to the first BigCo that comes by early on because they need the $$. While they neglect every other niche and business where it could fit like a glove.
Or more often doesn’t even bother legitimately testing it on the open market since their very limited programming time is spent serving BigCo and doing support.
A lot of companies using SaaS have a bunch of different systems interconnected with Zapier or their own systems. Which IMO is far more like Unix than x product that turns into a full blown CRM, CMS, ERP etc tacked on top a niche product.
Building highly customized software also generates tons of risk for smaller companies as it binds their entire revenue on the success of a small group of other companies who may die, switch core business, or get stolen away by a bigger enterprise software sales team.
I’d much rather build a niche software product and instead of building a CRM on top just add every sort of API, webhook, Zapier, or direct integration. Or isolate them into separate products with shared authentication and logging systems.