I have worked in companies which had monolith software, but they have been large and established businesses.

I will not name names, but I can say this...

All but one had constant, repetitive and quite painful failures, not fixable, it seemed. One company was an exemption, with some failures but a clear culture of pushing issues while implementing new features.

And one company I have been with from startup days till 150 employees had a microservice infrastructure, I have never seen so little downtime, such a smooth back office, front end, database, reporting system. The cto was owner and main developer, if something went awry, he would start working on the fix within minutes, no matter the day or time. The fastest issue response time ever. 2 lifetime downtimes of a handful minutes for the full service, and a couple components which didn't work for maybe an hour or sometimes overnight. I have to say though, when one microservice broke, it took down more tangential services than one would think, but other than that, hands down the best software I ever worked with.