MSE/Defender sure isn't enough for the ordinary user.
https://www.howtogeek.com/173291/goodbye-microsoft-security-essentials-microsoft-now-recommends-you-use-a-third-party-antivirus/Hence why Microsoft themselves has said
1] The detection rate is only tested with a small amount of samples.
2] It doesn't have e.g. IDP detection
3] It doesn't have smart/live analyzing to detect and block new threads.
4] It doesn't have a "sandbox"
5] etc.
Take other samples and the detection rate for a av at av comparatives will drop for MSE and go up for others.
The OP doesn't have a solution.
He only runs away from a problem but that doesn't make the (potential) problem go away.
I rather have a FP then a infection that is not detected.
Just make sure that you have a recent image of the drive and a recent backup of data.
If there is a problem the system can be up and running in 20-60 minutes again if there is a problem.
Don't forget that e.g. a power spike/drop, malfunctioning hardware etc. can also cause a system to malfunction.
And with millions of lines of code in Windows and all applications, a conflict/problem can (and likely will happen) sooner or later.