Since we're recommending alternatives, I've recently become a pretty big fan of Telegram
. It doesn't do video chat, but it does have voice chat (like phone calls, currently limited to 1-on-1) as well as "voice messages" which are akin to instant voicemail or, in other words, you record a message which the recipient(s) can listen to at their leisure in a non-real-time fashion. It also has other standard messaging/texting features and group chats and stuff like that. And it works on just about every platform in use these days. Windows, MacOS, Linux, Android, iOS, Windows Phone, or browser-based, wherever you need it, it's there.
My only real complaint about it is that creating an account is tied to a phone number. I think that's really stupid and would love to have an account not tied to a phone number. But the good news is that once you have your account, you never really have to use the number again. So if it were that important, I could have just bought a prepaid "burner phone" for 1 month and used it to activate my account and then never top off that phone account again.
Since the main draw of Skype is probably the video chats, often with groups of people, I can see how Telegram isn't exactly a replacement for Skype. But I used to be an avid user of Hangouts (and Google Talk before that) but Google's recent-ish changes to . . . well, everything, I guess . . . have made me start weaning myself off their services where practical. I've pretty much moved completely away from Hangouts except for when I need it for Google Voice. That said, Hangouts is still a pretty good solution for video chats, in my experience.