No job is perfect - a job that's never boring is probably one that's inherently stressful.

I think you'll probably need to say what you have in mind by teaching. Lecturing at a university? Subject teaching? Being an 'oral' (lol) teacher at a university? Adults at a language mill? Primary school? High school? Language mill kids? IELTS prep? They all have different demands and different level of engagement and skill needed.

I used to be one of the despised English-teacher-abroad contingent - I had a degree and a CELTA (still do, I suppose) and found teaching engaged adults to be one of the most interesting things I've done. You get a huge amount of human interaction, there's always a challenge and even if the job doesn't change the people in front of you do. I've also taught kids... not my cup of tea, although I was okay with those say about 6-12. Teaching little kids... shoot me! Teaching teenagers.. pas the vodka.

I eventually left teaching because, although it was enjoyable and the pay was okay, it wasn't going anywhere, so to a degree you could say I was bored although I never felt bored in class.

I have retrained and now work in a MUCH more stressful job, with massive consequences if I make even one small mistake, with targets, KPIs, deadlines, clients and corporate double-think to contend with. And that's enjoyable too - I like a challenge. But there are days where I'd HAPPILY go back to having a 12 students and the present perfect as being my biggest concerns.