I'm a similar situation. My current position has excellent work/life balance, excellent colleagues, interesting work in itself and I'm basically having fun most of the time. I would
not switch under normal conditions. The salary though has been stagnant for years and it has been my main crux for some time now. Being handled by HR, I also know it's essentially non-negotiable, despite not being an economical limit for the company. If I had a family or some bigger expenses (like a house or a new car) I would have to quit.
I'm actively looking, but no other job was interesting enough for me to consider yet. I won't switch for a job I'm "forced" to do unless it was paid at least three times my current salary, which would only be possible if I would relocate too.
It's sad really. A 10% bump in my net salary would keep me glued here for several more years.