I'd be dubious of sweeping claims about what is "crucial" to motivate people in general. I would also consider myself a gymrat in the sense you probably mean. I've been fairly consistent about lifting six days a week for roughly three years now. Time missed isn't down to motivation so much as travel, injury, and illness. I'm more than willing to accept that as a form of loosely principled periodization anyway. Cardio has been somewhat less consistent, but that has been far more down to what I imagined I was capable of than motivation. Now that I know I can do it, I've gotten pretty good about running from 20-40 miles a week or so with variance coming down to injury and illness.
This is all at home. My motivation is I'm an animal in a body that needs to be used and regularly stressed in ways it can adapt to in order to remain closer to peak functionality than degraded, and I don't want to degrade. I had very bad degenerative spine issues in my 30s and my experience living in a less degraded body has been far better than living in a degraded body. I don't feel any need for other people to push me. I work out completely alone in my own garage or on the street. I comment about it here when it comes up as a topic but don't try to be a part of any other web communities devoted to fitness. I don't publicly post progress photos or stats. I keep logs but only as feedback for my own planning.
This isn't down to trying to avoid other people, either. This is largely down to convenience. When I had gym memberships in the past, sometimes I would go and sometimes I would not and quite often the thing keeping me from going was the simple friction of needing to leave the house and get in a car for 20 minutes. As it stands, I didn't have a car for a few years and still very rarely drive thanks to the continuing spinal stiffness in the wake of multiple lumbar fusions. There is quite a bit less friction involved in walking downstairs whenever I happen to have a spare 40 minutes in the day.
I say all of this understanding not everybody works in the same way. Some may need a hard schedule. Some may need a coach or social factor. Some may do better with strict separation of home as a place to relax and somewhere else as a place to push bodily function. Some may need their garage for cars. Many are not going to have thousands of dollars to blow on equipment but can easily afford a monthly subscription to use equipment shared with others.
I'm only intending to point out there are many ways to make this work and to push language on the web away from saying things are "absolutely crucial to motivate oneself" because they worked for you personally. It was absolutely crucial to you. Something entirely different was absolutely crucial to me. What is absolutely crucial to some randomly selected other person who is neither of us I will not claim to know. If this is something you care about, try everything. Find what works for you.