Once you are a {something} dev, it is hard to leave.
That {something} can be web, embedded, ML, etc... it doesn't matter.
The problem is twofold.
First, your skills in {something} are appreciating more than the other skills. If you're a web dev trying to transition to embedded, the skills as a web dev will let you get a more senior spot than going back to a lower experience embedded.
As a $150k/y web dev, would you rather go to $175k/y sr web dev or $125k/y embedded?
It's not that its hard - just that the skills that you've invested time into don't have value and you're going to need to go back to being "just" a competent programmer who needs to learn the domain for anything you switch to.
Secondly, there's the "why are you switching" problem.
If you are switching from web to embedded, the question will come up "why are you switching to a different domain." When that question gets asked, many candidates exhibit a more whimsical or capricious nature of just wanting to do something different. At which point the interviewer is looking at "competent, but likely to leave in a year or two because they got bored" vs "less experienced, but interested in the domain." The second candidate is probably a better choice.
The way to solve that is the personal project and demonstrate that you're interested in the domain at more than a "I'm bored with what I currently do."
That {something} can be web, embedded, ML, etc... it doesn't matter.
The problem is twofold.
First, your skills in {something} are appreciating more than the other skills. If you're a web dev trying to transition to embedded, the skills as a web dev will let you get a more senior spot than going back to a lower experience embedded.
As a $150k/y web dev, would you rather go to $175k/y sr web dev or $125k/y embedded?
It's not that its hard - just that the skills that you've invested time into don't have value and you're going to need to go back to being "just" a competent programmer who needs to learn the domain for anything you switch to.
Secondly, there's the "why are you switching" problem.
If you are switching from web to embedded, the question will come up "why are you switching to a different domain." When that question gets asked, many candidates exhibit a more whimsical or capricious nature of just wanting to do something different. At which point the interviewer is looking at "competent, but likely to leave in a year or two because they got bored" vs "less experienced, but interested in the domain." The second candidate is probably a better choice.
The way to solve that is the personal project and demonstrate that you're interested in the domain at more than a "I'm bored with what I currently do."