Well, there's a lot of sides of it.

On the historical (And semi-current-ish) downside we had/have;

- lots of 'flash in the pan' stuff between 2008-2012ish (Silverlight comes to mind here)

- Anemic Entity Framework in pre-core, and the weird stuff EF Core had going on early in it's life.

- That constant worry as to whether you need to add .ConfigureAwait(false) to every async call in a library you want to open source.

- The thing where trying to do 'traits' in NetCore (Now that you can mostly mimic the behavior) has had some side-effects on performance, mostly resolved but still something you have to consider as far as impact. (To be clear tho, thank god, needed that...)

- WTF was that UWP workflow?

- Why can't we get a proper designer? I don't think it would be that hard especially given I can do nice things around workflow designers today. Speaking of workflows...

- The complete (what I probably guess was MS groups eating their own tail) thing where Workflow Foundation was almost truly productive, SSMS had a thing based on it that was surprisingly productive, and it has been murdered instead of getting the TLC it needed to really disrupt. This one is extra loud because it is so similar to the 'low code' platforms so many orgs have sank money into.

- Less impactful as far as people eating the lunch microsoft left on the table, but WCF.

The upshot is;

- If you're willing to do some looking there are great options out there. lazy example, linq2db is basically a DSL that is close enough to EFCore as far as 'how you compose' that you can teach it to a group of WITCH devs in 30 minutes or less.

- It really is easy to do all sorts of stuff. It's just productive.