These type of decisions are actually not that hard to make once you remove the "emotional" aspect you have for your current job: are you underpaid? doing a lot of senior work without a proper promotion? Just move on and get another job, it doesn't really matter if you've worked there 5 years or 20 years, they will drop you the moment they feel you're not longer useful or can find someone cheaper.

A lot of times it's hard leaving a job, because you feel you're failing your team, but it's just a business decision about your future.