Very vague and large question but: How do you become better in terms of software development / engineering?

For context my current job is pretty good but sometimes it lacks challenges, I’m interested in how people become better out of the work scope I guess.

I avoid spending too much time improving my skills outside the work context. Instead, I try to find ways to improve code quality and workflows of the projects I’m working on. It allows me to kill two birds with one stone as I usually end up learning new things in the process while improving the products I’m working on

learn how to:

* use search engines

* read and understand manuals

* ask good questions

* critically consider your own ideas and challenge them

Pain and Suffering.

Read other people's code.
Read about solutions to difficult problems.
Revisit the basics from time to time. The state of the art is constantly changing.

Here's what I did lately and it seems to have improved how I think about writing code in general -
There are some core principles like SOLID, KISS and DRY that make you a "senior" in terms of code quality - you should definitely start familiarizing yourself with these in the language you're currently working with. Well known patterns work for a reason :)
There's also a guy I know who draws diagrams of different components and their interactions and only once he's figured it all out does he actually start writing code. That makes his code super clean to look at (as he follows well known patterns like MVP or any MVx for that matter).

certifications, bootcamps(real ones, no the shit from tiktok), books (concrete math is my personal challenge), freaking hackerRank.

Honest answer?

Really really really honest answer?

Embrace the madness.

Make 8 hours a day. Sleep well. Eat well.

I'm these 8 hours, do any insane shit task noone wants to do for reasons.

Defucking that 1200 plus dependency framework noone dares to touch? Yeeees.

Reverting the 10 MB file with 10_000 classes that were once autogenerated, then manually edited over years to being autogenerated? Of course!

Writing the universal conversion framework that takes markdown, create an universal syntax language for formatting and description in different output formats and exporting the MD to e.g. heavily formatted Excel or plain CSV or XML or YML or HTML... Sure, why not.

Just. Embrace. Madness.

You'll learn a lot, especially that sanity isn't always a necessity.