I’d also add sporting equipment such as mountain bikes to the list. A bike that is marketed as a “mountain bike” may be fine for cycling on paved surfaces but not be entry-level for actual mountain-biking, i.e., be very unpleasant – or downright dangerous – for off-road cycling.
My strategy for starting new hobbies is to research as much as possible, talk to friends who are already past the beginner stage and – if possible – borrow equipment from those friends. After that, try to buy second-hand. Whether or not you keep up the hobby, you can sell on the original equipment. And if you decide to keep with it, you have a better idea of what you want/need when upgrading.
+1.
Although the saying is "a bad workman always blames his tools", but I often heard the notion that a beginner should be trained using tools and equipment of decent quality, so it doesn't mislead the beginner or interfere with the learning process. After one has mastered the skill, one may choose something worse later on if budget is an issue. At this point, the limitation of the tool is more tolerable, since you already know how a task is supposed to be done properly, you only need to overcome the deviations.
Of course, this strategy is more suitable to the trainer than the trainee - it can only save money for you when you are trained at workplaces or institutions, where you don't need to pay for the equipment...
It seems like you're drawing a direct causal relationship to what is a very complex chain of events over a long period of time. How can you be sure the problems would not have arisen regardless of what tool (shoe) you originally bought?
I was too young to understand quite what the problem was, or to save up enough money on my own to upgrade, so I ended up quitting lessons altogether.
Or if you're really dedicated to saving money, you can always pick up the almost entirely separate hobby of doing guitar setups yourself, but that's probably not worth it at your current stage, based on how you've described yourself.
In the case of this guitar though, it was really the cheapest thing out there because I am on a budget (and a really tight one), so any real work done on it would cost more than a few times the guitar itself and more than I can afford to dedicate to it. My actual guitars are an ocean away for the time being, but I'll still get them back eventually. In the meantime I have a nice decorative thingy I can pick up sometimes, and I try to remind myself that now that I'm "more experienced" I should take this as a challenge rather than an excuse.
Additionally, in the guitar example, you learned how to play and learned what it meant to own a decent guitar. Then, when presented with the opportunity to buy a new guitar: bought a crappy one, ignoring everything you had already learned about the instrument.
Given that you were so easily discouraged from learning the guitar, it's also equally likely that it wasn't something you were truly passionate about and gave yourself an excuse at every turn as to why you weren't progressing.
The original advice was to buy the cheapest thing and just use it. GP's advice was "Sometimes you don't know what the minimum viable is because you are a beginner and don't know yourself well in that field."
GP then gave specific examples of cheap products that aren't particularly suitable for beginners: (1) cheap running shoes that lead to bad habits and possible injuries and (2) cheap guitars that are difficult to play. For both examples, he described how as a beginner he lacked the experience to know what he needed.
For example, I started running with shoes that were somewhat fine for beginners when I would double-check online, but happened to have limitations that affected people who practice a lot, or people who don't practice properly, or in my case undiagnosed issues (hypermobility of the knee). In my case getting those shoes with too much shock absorption was actually dangerous because it prevented the feedback loop of auto-correction from being built. This led to some habits that I didn't notice were bad and later on led to a pain in my knee that has, despite my best efforts and much rest over the last 8 years, entirely prevented me from the freedom of running.
Another example I've encountered is with the guitar: the first one I picked up was this entry-entry-level thing that was viable for my budget but hindered my interest in practice because I didn't just encounter the physical pain you encounter when learning the guitar, but also the pain you get from badly adjusted guitars with high action and uneven frets and fairly crappy wood. I gave up on it a few times. But I eventually tried again and made the hypothesis that the hindrance was the guitar, and after testing that hypothesis I committed to buying a better one which enabled me to actually learn things that flat out seemed impossible on a crappy piece of wood. Years later, I'm far away from all my good guitars and I buy this entry-level thing because I miss playing.. and it's been hanging there mostly untouched because of how bad it just feels.
I think it's much smarter to spend some time testing out things with other people's help and to borrow stuff for a while whenever possible, but on average to commit to something above entry-level if you're trying to be serious about anything. You'll save yourself a decent amount of time, you can give yourself a progress curve that looks much smoother, and when comes the time to truly upgrade you'll have something solid to use as a base to look at higher quality tools.
edit: notwithstanding the fact that in many cases you have zero resell-value for physical tools that are entry-level, while something average will at least go for a reasonable percentage of the original price