I've already seen several internal tools becoming a burden for the company that has created them. Development is costly and the resulting product is often buggy, unreliable and demands constant work and attention.
Is that a common thing? Is it a bad idea by default for a non-technical non-SaaS company to hire developers and build anything custom?
I would say this is even common in technical companies.
Many tech companies suffer from NIH syndrome, and needlessly re-invent things that already exist elsewhere, or are not part of their core business. I've witnessed it many times. I would say this is especially common when the company has too much cash on hand and can squander it...
Without any data you will not get any proper advice. Everything is matter of scale, rate and how dynamic your domain is. Sometimes choosing 3rd party is better sometimes creation of own IT.