Theres nothing wrong with using them. Just don't use google's You can also self host your own link shortener & be your own provider theres tons of link shortening scripts that are ready for self hosting.
Discussion
Vyram, the problem is that no matter which link shortener you choose, you add another point of failure for link rot compared to sharing the link as is.
That all depends on your viewpoint. Sometimes you can't share the link as is because of a character limit which is why shortlinks were invented in the first place. : )
Also if you are hosting it yourself the only point of failure is if you fail to pay your bill to the hosting provider. Or if you make the decision like google to just stop doing it you don't have to rely on a third party website when you can host one yourself & rely on yourself.
But if you can't do that then expect this when you are using someone else's service it's their decision not yours.