Let's say you work at a big company in an environment that does not prioritize testing. You are heading into an interview at a smaller startup that LOVES testing. When one of the startup interviewers asks you how you feel about testing, they want you to answer the question in a way that makes it sound like you'd be enthusiastic & competent at testing "all the things". If you say "I don't have time to write tests at work", you're almost certainly not going to get the job. If you say "I love testing, I write tests whenever I can, a certain employer I may or may not currently work for makes it hard to me to increase test coverage, and that's a factor in why I'm taking the time to interview with you", you're going to almost certainly get the interviewer's attention in a good way. The other part of selling yourself is that you, as far as this employer is concerned at least, really need to love testing.
Get it?
So what does it take for you to look & sound like the person who would get the job at Amazon, Cloudflare, or Coinbase? What does it take to be like what you sound need to sound like? Can you get that experience at work by taking initiative? For the experience you can't get at work, what can you do to get it outside of work? Do you need to buckle down and tear through Cracking The Coding Interview & LeetCode exercises? Do you need to work on a personal project that showcases the skills you can't develop at work? Figure those things out as best you can, push yourself super hard, and you'll get one of those shiny jobs that breaks you out of your current career paradigm.
Also, don't overlook the value of being really good at something people really need. That's a basic supply and demand thing. If you're a badass VB6 developer or MUMPS developer, those are simply not a hot skillset for almost any employer these days.