I see two issues in the quote:
"If one isn't passionate about ones practice, one should quit and find something else to be passionate about. There's little or no benefit to be had from training sporadically,... making less than a committed effort to master the art."
First, there's the problem of "passion". I occasionally I run in to people who insist that I must be passionate about what I do, who see "passion" where I just see something I'm interested in and kind of like. I used to make pottery, farily seriously, and when I quit this crowd went up in arms, "Oh NO! But that's your passion
. Don't you love it?" No amount of explaining could convince them that I was not at all upset about losing my art, that I was making time for other forms which had become much more important to me... but I wouldn't necessarily describe myself as passionate about. 8 years later, some of my colleagues from the craft shows still give me a hard time about it, and I feel that it's a totally unnecessary guilt trip, even if they're trying to be supportive. I think it's more than possible to be serious about practice without being fanatical or passionate.
Sporadic training is more of a real problem, as far as I'm concerned. I know several people who come and go, practice twice a week for a few weeks, then don't show up for months, then come back for a while, and fade out again, show up once, aren't heard from for a year, etc. It's almost impossible to progress and develop in the art, on the way, with a training pattern like that. I think you do need to make a commitment of at least twice a week to stay on track, and 3-4 times a week to progress but
you do not need to center your entire life around aikido, non-stop, over the course of decades. If you're going to keep it up long term, there will be times when most of your energy and attention is focused on other areas of your life. The question is whether you should stop practicing durring those times (because your "passion" is elsewhere) or keep showing up until your "passion" returns (particularly if "mastery" is your goal, you won't get there without showing up consistently over the couse of decades). I think you should keep showing up, most of the time, because inconsistent training is just too frustrating, and it becomes too easy to make excuses to not show up.