For me, it stopped doing what it always did for me, when MS bought it.
It used to be dead simple, make calls on shitty airport wifi. Chat messaging that worked reliably.
I used it for dead simple group messaging at work and personal use - desktop, laptop, phone. Send a message and it'd arrive.
Then in something like 2015 that all started to break. I'd send a message from one computer, and it'd only deliver to one of the recipient's devices. Then the replies from that device would only go to one of mine.
Neither had complete message history. Sometimes they would sync up, but then other times not.
It resulted in an argument with someone who thought I was slacking off and ignoring them. It took comparing message history in person to find out that half the messages I sent them were not on their device and vice versa. Even signing out/in again didn't show the missing messages.
Calls started doing similar things where I'd call someone, it'd time out. I'd message them asking to call me back when they were ready, only to find out that they hadn't seen the call come through at all and were waiting for me to be ready.
Eventually we gave up on it for work - moved over to Slack for messaging and something else for voice when we needed it (This was before Slack had voice functions).
The few friends I still spoke to on Skype went over to something else, too.
So, if someone suggested connecting using Skype I wouldn't laugh at them, but I also would suggest just about anything else.