I don't see how using credit to buy mods is different then the credit/loan that was used to get the car in the first place. Credit has to be paid back, so it's def not the free ride the OP seems to mistake it for.
On a more "real" note, credit may be the only way some guys can afford to get to that place where they hear the exhaust sing and the rear tires break traction sitting in the only seat in the world where they feel whole. If you pay it back, who the fck cares if it's bought with plastic.
The differences are in how you view that credit, how extensively you use it, and how you handle it.
Buying on plastic because it's a convenience that you can pay off in a couple of months is one thing. Letting it sit there costing you big finance money every month because you're barely paying the principal down is financial suicide. That was a sucker's deal to get yourself all wrapped up in even back in the days when you could count on your job being rock-solid stable and annual raises were all but guaranteed.
For about the first 20 years out of school - my degree and my marriage are both date-stamped 1970 - I know we didn't put any car expense on credit other than the purchases of the cars themselves. And I built/rebuilt engines, swapped powertrains, and upgraded suspensions pretty much when I wanted to or needed to because something broke (big hint here - learning how to do all of the work that doesn't require major machine shop equipment is huge in more ways than one). We didn't even hold a major CC to put automotive parts expenses on until I was almost 40, and to this day I'm a cash customer when it comes to gas, entertainment, and most of the smaller car-related expenses.
I still won't carry a CC balance on automotive parts, online track day registration fees, or the few diagnose & repair tasks that I've farmed out over the last year or so. I can see three sets of tires (likely Michelins) and one set of wheels (18x10" or wider) happening in the near future and even though I'm mostly retired I won't be financing any of that.
What I hope for you younger members is that you can manage to get your houses paid for and your kids educated/married off with a few years of good paying employment still ahead of you before you retire. Don't let being "car-poor" get in the way of this. Not having those expenses will go a long way toward seeing you through any lean times later in life. Never mind how I know this, just take my word for it.
Norm