These are only my opinions:

I think the issue is "phase changes" are always going to be tricky in any community, and the path an open source project takes always includes one or more phase changes.

Aspect 1: Tinkerer vs User.

By their nature, most FOSS projects start with a person who wants to solve a problem for themselves, rather than as a business idea. This attracts the sort of person who is maybe only vaguely worried about solving that problem, but is very interested in the solution itself. Or maybe the tool does 90% of what it needs to for this new use-case, so a tinkerer is happy to go in and add the extra 10% themselves to get it to work.

But at some point along the line a project becomes popular or useful enough that Users show up. And Users want something fundamentally different than Tinkerers. They don't want to work on the project, they want to use the project as-is to do some other work. It's just a tool that allows them to accomplish what they're really trying to do. And the Tinkerer mindset that got the project to here is fundamentally incompatible with the User mindset that allows it to grow outside a small group.

It's important to note that almost everyone who is a Tinkerer in something, is also a User of other things. Maybe I'm working on this project, but my editor is just a thing I use. I need that to work without me thinking about it, so I can get the other work done for the project I do care about. And if I'm tinkering with my editor then I need my kernel to just work. Or my hardware. Or my internet. Or my electrical grid. These were all things that somebody once tinkered with, that now I'm just using, but that transition is fraught.

So if I'm Tinkering with a Linux phone, I'm more tolerant of issues, I'm invested in the project improving, and it's fun to overcome limitations. This is essential for the project to start and progress, but there will only be so many people interested in that. Everyone else is a User who just wants to read their emails at the grocery store, and is pissed when that doesn't work.

Aspect 2: Hobby to Job.

At some point most FOSS projects are an intrinsically interesting hobby, but the idea of financial support makes them an extrinsically motivated job. Studies have shown in a lot of cases being paid to do something actually makes it less enjoyable or interesting, even when it's the same actions in both cases. So there's that paradox, my job takes time away from this hobby, but making this hobby my full-time job makes me want to do it less.

But even more importantly at a project level there's a phase change around funding. Most of these projects when they're just a few people in their spare time, have no need for money. What does $7 a week really get me. Sure it's "support" and "thanks", but it doesn't do anything to shift how this project fits into my life. Then that grows to $100 a week. That's money, for sure. But it's not "quit my job" money. So I get this money, it helps with groceries, but still doesn't produce more time to work on the project. At, like, $1000 a week, now I can maybe quit my job if I live in certain parts of the world. Everything up until now is kinda "nothing" and then it's only when we get here that suddenly "something" changes. Phase change. But I still can't hire a second person. And until I can, any extra money is more income for me, but doesn't really help the project either. I'm already full-time on it, and $1500 a week doesn't buy me more time.

So because of that phase change, when the project is small it feels like there's no reason to go through the work of setting up donations or subscriptions or whatever, because it's a hassle that's just going to get me, like $7. At first.

Aspect 3: Project to Product.

Like the Tinkerer to User spectrum, but for the community as a whole. When we're all working in our spare time for free, giving the result away for free is easy. And it feels good, because we're a community. But at some point in the future of this project, one can imagine a point where there's a company that sells this product for money or makes money off it in some other way.

But when? We're here, that potential future is there, and like with Hobby to Job, there isn't really a smooth line between the two. It doesn't feel like a Product now, I'd be embarrassed selling this and I don't even know who'd want to buy it. But if it's ever going to be a Product, someone's going to have to buy it. Someone's going to be the first to buy it, even. Who? When? How? These are answers that will have seemed obvious in retrospect, but are perhaps impossible to tell in the moment.

And what's worse is that the skills it takes to sell things to a company are different than the skills it takes to Tinker. In some ways even opposite skills, given that the Tinkerer just wants other people to be interested in what they're interested in, and wants to give it away for free. They want to spread it without restriction, that's why they started working in a FOSS thing in the first place! At which point does that person decide to charge someone money instead.

And what's even worse than a User is a Customer. Where a User might just want something to work, a Customer feels entitled to the thing working. What else did they pay for, if not a working thing. But $70 is a lot of money for a Customer to spend, and not a lot of money for a Tinkerer to use. So the amount of entitlement the Customer feels outpaces the amount of value the Tinkerer recieved in trying to bend their project to the Customer's demands.

And as the company gets bigger to support more and more customers, you start needing lawyers and HR and payroll and support people and graphic designers etc etc etc.

This is partly why so many tech projects are picked up by already established companies and deployed as part of their product. Because they already have all that crap the Tinkerer doesn't like thinking about, and the code is freely available for the taking.