Lotsa possibilities for making and marketing a product. Problems, for sure, but all solvable. If it was easy, everybody'd be doing it.
There'll always be people that take up time and don't lead to direct payment. Most of them well meaning. One always has to do PR, accepting payment can happen in a multitude of ways, development is expensive, marketing takes time and luck is involved. Evolution and problem solving is something us machinists are pretty good at with materials/machines, but maybe not with people. Garfield is clearly good at it, but someone who has a history of only making parts for others and has to see the money immediately is going to have a difficult time.
I do both job shop work and make a tool/product for a niche market. It's a good balance for me - job shop work is available and fills the schedule as needed.
There are competitors that I have to stay ahead of - I think of us as a collective, striving towards excellence

, however, my competitors do not - one was pissed that I "stole" his design and demanded royalties. I didn't realize I had at the time, was only duplicating and improving what a customer told me was no longer available. I took pissed off man seriously till finding he had no patent and that he had only "improved" a previous design, primarily for price point and ease of machining. Meanwhile the designer whose work he copied is still pissed at both of us but was not above incorporating some of my improvements into his latest design. He's so mad that he won't sell attachments to anyone that owns my tool, even though they interchange.
So first pissed-off-man designed an even cheaper tool, ordered parts in big quantity then promptly died, sticking his heirs/company with parts for 500 tools that no savvy user will buy because they're time consuming to set up and hard to keep in alignment, all out of spite.
A long story, but this is typical of product development and sales, far as I can tell. One has to stay ahead of competitors and sales and marketing is to be learned. If you aren't willing to take it on, don't do it. It's not for everybody, but I think it's a ton of fun.
I sell both direct and through a distributor that's passionate about his business, has used the tool for years and is very upfront with me about what works and what doesn't and suggests improvements. I'm lucky to have found him and he thinks the same of me.
So yeah, if you have a product you think will work, go for it and do it in a way that suits YOU.
Anybody ever dealt with the general public? In case you don't know, the customer is always right, do you have the people skills to deal with that attitude? You want them to come to your shop to look at the product and waste half a day trying to make a sale? Oh, okay, sell online. They pay with a credit card or Paypal and want to return the product for refund, how do you handle that? Credit cards and Paypal favor the customer in a dispute. Warrantee on the product? Liability insurance covering the product? How about product support when customers can't make it work?
In the unlikely event the product is a big seller how do you protect against others who will for sure copy your product? Patents, copyrights, can you afford to defend these?
$10 or $1,000 product? Let's say a one man shop, full time might need to gross $100k/year (gross, not net). With a $10 product you need to sell 10,000 a year, that's 192 a week, can you pack and ship that many? $1,000 product, how many impulse-buy in that price range, you need to ship two a week?