3D Cartoon Graphics. Default Materials in Unity, Maya, Blender etc. Do I need to learn shader coding?

If there was a Stack Exchange for CG, I would post there instead. But since there is not and I know there are a lot of knowledgeable and very helpful people here, I thought I might save a lot of time by asking you all.

I’ve been working on lots of game ideas (I am trying to do all coding AND graphics alone).
I really want my games to have a distinctive look to them but I am struggling, all my games end up looking like a mix-up of other peoples graphics. I do realise this is due to my inexperience and inconsistency in the modelling process mainly (and laziness when it comes down to UV mapping and other bits, however with that said, some small projects I have really tried to make everything to a high cartoony standard).

This is one of my games that is closest to what I want. But sometimes it just has that “default Unity look” to it (I wish I could explain better!)

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Then my more recent WIP:
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So my question is a broad one. I’ve studied top-end games (and other indie ones) to try to notice differences. I mainly see there is a kind of outline around the characters:

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Things I notice are the outline thing, the shadowing on the characters, and actually the quality of the environment graphics work. The games in my screenshots (that I made) I want to continue working on them to make them look better. I realise I am not gonna fumble around in Unity and make something on a par with Legend of Zelda BOTW, but I would love to learn some of the techniques used, particularly ones that can be done in Unity.

I am wondering if I need to learn shader language or perhaps Post Processing techiniques. Or am I wasting my time in the basic Unity and do I need to study the HD Render Pipeline (etc, all the new stuff I am so far yet to look at)

Your advice and insight will be a great help to me. Many thanks