The only way to massive success is compounding.
This is a truth that is inviolable.
Each and every single success, in whatever field it may be, is the result of compounding effects. One-off events with no prior build-up (eg winning the lottery) will fail eventually unless it piggybacks off of something else that was compounding before the event (eg fiscal responsibility).
The compounding effects of a project are worth infinitely more than skill development, unless skill development itself is the project, as is the case with research. Most other pursuits have a manifestation of progress outside of the accumulation of knowledge — how far your product has come in a startup, the number of projects in your portfolio if you're an artist, how much of your movie has been shot and edited if you're a filmmaker etc.
The default pathway for most individuals until they graduate is (supposed to be) skill development. That is the entire point of the educational institution. In reality it tends to degenerate into a status game that more resembles building up infinitely many safety nets instead of any wholehearted pursuit of knowledge for its own sake, but even if everybody that went through the educational system tried to maximise skill development, they are ultimately still only resources.
The generation of human capital is fundamental to the advancement of projects, but developing the capacity to conceive of projects is itself not a priority for the educational system. Given that most individuals tend to optimise for capital the majority of the time in higher education, why the pretence of knowledge development anyway? I assume it's because the pursuit of noble goals like the acquisition of knowledge tends to be a status symbol. But I digress.
The primary question I'm interested in is the right balance between the compounding effects of skill development vs the compounding effect of time spent in the pursuit of a project.
There are certain assumptions underlying the relationship between skills and projects.
Assumption (1) is obvious but rarely helpful. Unless you are developing skills in the context of maximising future choice and maintaining optionality (ie developing skills in the absence of an applicable project), the question that's infinitely more applicable is "What is the appropriate balance of skill development and pursuing my project to maximise the progress of my project?"
If the project is worthwhile in scope, there is a very high probability that it is at the very edge of your capability. For projects that are aspirational in nature, you probably don't have any of the foundational abilities required to pursue it at all. In that case, your primary concern should be getting up to the minimum required threshold of skill development as fast as possible. This threshold is defined as the amount of knowledge required to determine a rough direction of progression on your project at the current time (you can cap this at an arbitrary certainty: say if you know enough to say you're ~70% sure that the proposed direction is the correct one).
Past this threshold, the difference between skill development and the pursuit of your project is a false dichotomy. Any sufficiently challenging project requires the acquisition of skills that are applicable to problems that only arise in that specific project — for example, if you're building software and you have to learn how to use a specific library for some desired ends, that skill development is probably only local to that project.
In short, if you know enough to know what the immediate next step is on the path to your end goal, you should start chasing after whatever goal you may have by taking action. Any more information is unnecessary and more likely to lead to productive procrastination or analysis paralysis.
If you do not have a greater project for your life apart from immediate societally imposed concerns, then you have no choice but to embark on a journey of discovery to understand what it is exactly you want to dedicate your life to. If you are aware of the fact that you have no original motivations and are fine with the fruits of following societally defined reward landscapes, that is fine as well. I will write about this at a later time.
Anyways, if you've been wanting to pursue something for a while and have been using "developing your skillset" as an excuse to not work on the thing itself, take this as a sign to do the thing.