So, you want to improve as an author. Unfortunately, art has no objective value and therefore, there is no One True Path to Good Work. But I run this blog for a reason so I won't stop there! There might not be one certain path, but the one of self understanding. What is important to improving your skills is not how well you can follow an arbitrary code of advice, but understanding:

• your own intentions, both as an author and in a particular work
• a wide range of techniques and what effect they give the work

i. Your Intentions

Intentions can vary both on what you want to have in all of your work, or in a specific piece. At the least, you'll have artistic intentions:
I want this novel to be dark, brooding, reflecting on the darker sides of human nature.
I want this graphic novel to be a lighthearted spoof on nature magazines like NatGeo, but if they were made after a nuclear holocaust.
Some considerations here would include:

• mood
• writing style
• genre, and within that combinations of different genres or subversions of genre
• what story elements you want to place a lot of focus on (eg. character psychology)
• any specific idea you really need to be there

You can also be like me and have strong opinions. This would lead to intentions that have ideological grounds.
I want this novel to be a dystopia that satirizes Stalin's USSR and its hypocrises.
I want this novel to question how a democracy can allow for people with wide-ranging and unchallengeable power.
I want this novel to include positive depictions of butch and gender nonconforming women.
Some considerations here would include:

• Political issues you know and care a lot about
• Questions of morality you want a reader to have
• Classes of people you belong to that are rarely depicted with depth or sympathy, which you would like to change

ii. Techniques

Okay there's like, way too many techniques to even mention here. Go check out this blog or a library or smth. But being serious, we've all been given advice about specific writing techniques or tropes being inescapably Bad. Maybe it's infodumping if you're a fantasy author, or good-guy-bad-guy love triangles if you're a romance author. If you've heard any of these, it's time to learn to unlearn how sinful they are. Nothing's universally bad, but has some effect over the work. You might realize you like that effect, or you might not. Some choices are cliche, but that in itself isn't bad. A lot of people don't like certain cliches, and a lot of others do. Popular storytelling tends to be repetitive in its devices. You should take authority over your own creative decisions without worrying if one less person is going to pick it up for completely arbitrary reasons.

Most likely, you're not gonna go into a piece completely blind and starting with your agenda list. Do that, if it's your jam – but this should be visited and revisited through the writing process. It is more convenient to make a specific agenda of the points that matter to you. If at the end of a more final draft, you don't feel like your work matches up with this agenda, ask yourself why that is: did your creative vision change, or did something fail to match up? It is completely okay either way, but you should search for an answer. Hell, if you've spent as many hours as I have on my work, you deserve to feel satisfied with it!

What does changing your priorities look like?

Here's an example: Someone wants to write a novel. Her original intention is to create a fantasy novel with vast, expansive worldbuilding. After reading a late draft, she feels dissatisfied. She might feel one of two ways:
*During the process, I learned a lot more about my characters. I feel a lot more attached to them than just the world. I'll re-focus my story around the characters and keep the tidbits of worldbuilding most relevant to them (or what I think is cool).
During the writing process, I strayed away from adding too many details of the worldbuilding at once. I was afraid that if they're not plot relevant, or if I go on too long, than it's 'infodumping' and my readers will abandon my book with great shame. I'll add whatever I like whenever.
(Craft-advice-givers that say infodumping is bad in sf/f.. what are you doing? It's like going into IKEA and complaining that they're selling too much furniture. I should write a rant on this)

Good critique should help you get here: someone appeals to your intentions (either because you've already stated them or they're guessing) and offers some change that they believe would support it better. The point of critique is to make the work a better version of itself and not change it fundamentally. This actively involves seeking comments from you, as the writer, as you understand what you want from your work the most.

This line of thinking also counts in self-critique: would making this change help make my work stronger? Does it make it more approvable in the eyes of some council, or does it make the work stand strong on its own? Even if you write with the goal of publishing, this holds true. You will still face a lot of rejection anyway, and the type of work they would like (outside of arbitrary meters) is a work that knows what it wants.

Am i giving you answers because I am a goddess of writing? Of course not. I don't know even close to everything, and I constantly see myself improve. Anybody who tries to pitch advice as if they know everything is either being dunning-kruger'd or is super pretentious.