Where I'm from (Norway), job hopping every year or every two years, would look real bad. Software Engineering IS a bit more forgiving, but you're still going to get asked "why have you switched jobs five times, since you graduated in 2017?".
In fact, there's a real chance you wouldn't even land an interview. The employer is going to assume one or more of the following things
A) The person gets easily bored, and constantly needs fresh and stimulating work.
B) The person does not (easily) get along with people, or has problems with settling at a workplace.
C) The person is constantly being let go / can't hold a job.
D) The person is very salary/compensation focused, and will jump ship on the first chance.
Hopefully some of these things will be uncovered when contacting references - but there are lots and lots of former employers that will cover up for a bad hire, just to be polite. Or the bad hire is very good at picking people to use as a reference.
So you're kind of stuck with a candidate that's either job hopping because they want to "level up" as far as salary goes, or some other underlying reason they can't stay.
If tenure over 1-2 years is of no importance, then that's obviously not a big deal. There are businesses, ranging from startups to mega corps, that just need warm bodies to power the various projects - easy come, easy go. Be productive from day 1, and work them as much as they can.
But for highly specialized firms and positions, where you spend the first N years on training, job-hopping candidates could be completely unacceptable.