That's a very simplistic view.
Like with all things, there is a point where more investment money does not make things faster or better. In fact, since pretty much everything is still dependent on people and social groups, if all the relevant people are already busy, you won't get much for your money.
And too much money chasing too few choices creates bubbles, wich is exactly what has happened. And not just in tech, it is the problem of real estate market in many places of the rich world, and similar bubbles can be found in many markets.
I believe it is actually one modern problem, a good part of the rich world is getting paid a lot more than there is really a need for; and since we glorified "investment" essentially has a way to make even more money; a too big amount of money is not doing much instead of being useful right now.
If you look at society as a whole, spending every ressource every year would be bad, but also setting too much aside for later is actually wasteful.
It's a lot like stocking a pantry, you need to put enough so that you don't run out of food easily but if you have stuff in there that hasn't been used 5 years later it shows the "investment" was too much.
Food gets stale and loses nutritional value over time (even canned) but money also gets stale in a way.
As for the startup vs yacht I would say it largely depends on how useful the startup can ultimately be to society and how many people it can employ (how much actual value is being created).
Because even though yachts have fossil fuel consumption problems, it actually takes a lot of people to make them, maintain and service them actually. It can potentially have a better social impact than a startup...
And this is the root of the issue, people getting a lot of money actually have a responsibility to redistribute it (in an intelligent manner preferably); but what is happening is that people try to get even richer even though it stops having much value to anyone.