Maybe I am sort of fresh in the workforce (3 yrs) but I just don't allow this - if I am not in the office I don't work. I don't have slack on my phone or whatever and I have strict boundaries working 9-5. Does it become worse when I have more exp?
But most of this is self-inflicted via tacitly accepting and reinforcing cultural norms that don't actually need to be followed. I've yet to work at a place that attempted to abuse my boundaries once I made it clear I respected them. I.e., "Didn't you see that email I sent last night?" "I did when I got in today", they now know I don't check email after hours. No one wants to 'officially' say "You should have no work life balance; we expect you to be on call 24/7", so just making it clear that you won't voluntarily do it, and will presume that you are always truly off the clock when not at work, means they tacitly accept it.
I keep weird hours due to working remotely and across time zones, and I do encourage people to contact me by phone for anything time-sensitive when I'm offline. But that almost never happens, people are usually OK with waiting until I get back online to answer their queries.
Some form of this is more the rule than the exception on my team, because the people who don't work remotely still have lives (pick up the kids, avoid the rush-hour traffic, whatever) -- and also have to be flexible about their hours due to the multiple time zones.
This includes people with 1 to 25+ years experience FWIW. So I wouldn't worry about it, if you want to have a strict 9-5 boundary you can find good places to work (just not on anything mission-critical). If you prefer to work 40 hours a week on some other reasonable schedule, you can also find good places to work.
I once had a colleague who worked a very strict 9-5 and could have been called in an emergency but we all understood it would have to be a REAL emergency before we bothered that guy. He did a great job and everyone respected him, despite his being probably the only guy in the building keeping such a rigid schedule.
It's painful to watch. Glad to hear you're not falling for it.