I honestly really agree with the previous users, but here are my own two cents too
Is there a way to tell if a character is cliched?
I usually take a tour on tvtropes and try to find as many cliches as possible that fit the characters. Otherwise I think most people recognize cliches by the virtue of having consumed enough fictional content to be able to see clear patterns that keep on repeating. There are also a couple of tests online regarding the "mary sue" qualities in case you want to test your character and perhaps get a different perspective on them. It's worth noticing though that I don't really subscribe to the whole oc elitism where mary sue hate kinda stems from, and I think people should just make the OCs they enjoy! The more you work on characters the more unique and balanced they become with time!
And does it really matter if a character is cliched?
To me it doesn't really, by default. Cliches are cliches because people like them: they're very often universal and can even be things real life people also repeat or perform in their lives. Cliches are simply patterns, and by itself the concept of cliche is pretty neutral. It's true a character burdened by a myriad of cliches can come across as very flat, predictable and by extension disinteresting or frustrating, but I genuinely think it's more about how you choose to write those things. Some of my favourite characters ever actually play with tropes and cliches by taking the basics and then intentionally turning them around in an interesting and genuine way (like a prince coming to save a princess, only to realize she needed no saving, and ends up understanding and even accepting he is actually the one who would have needed help a long time ago & learns to reach out for others)
Does a cliched character mean that you’re a bad writer?
Not necessarily! I think it's actually very clever if a person is able to have a character ridden with cliches, but writes and portrays them in a fresh and different way. Being aware of cliches and using them for your advantage are something I actually really look up to in many writers.