Tails don't wag, dogs do
Knowing what you can and can't control helps manage expectations. Over time, you can look for ways to incorporate some of these factors into your circle of influence.
Asking the testing department to shift left or improve quality is like asking a dog's tail to be responsible for wagging. While tails do an excellent job of the mechanics of wagging, it's a dog's brain that controls the activity.
In the same way, software testing is fundamentally an activity constrained and resourced by product owners and engineering leadership. Software testing rarely wags its tail for its own delight and instead serves a purpose dictated by others.
Quality at senior leadership
This is why it is so important that there are advocates for quality at the leadership level. People who can explain the how and the way of software testing. People who can advocate for more time, budget, and engineering ownership.
This person can have any title or role, but the more senior, the better. For instance, they could be a product owner or head of engineering. In some cases, it's a senior quality professional who performs this role—someone who is on par with other senior engineering leaders. It doesn't have to be; it could be engineering or product leaders who are passionate and understand the nuances of quality beyond "automate all the things".