Investing in a fixed asset is investing.
That's great. Does this particular form of investing help the Greek economy?
But still, it logically follows that if the only way to unlock prosperity is taxing rich people you'd want to have lots of rich people.
Only as a poor second to a more even distribution of resources in the first place.
Thus with no rich people to tax your economy falls apart.
You're not making any sense. You have to tax people with money. If all the money is concentrated in a few rich people, then you tax them. If the money is spread over more people, then you can spread the tax burden over more people. Most income tax systems manage this automatically.
What's happened in Greece is that the money has gone to rich people via corruption, and to Germany via sharing a common currency, which acts to raise prices in Greece and lower them in Germany. The EU's plan was to use the extra borrowing and fact of EU membership to stimulate growth to make up the difference. Unfortunately it didn't work.
Greece collects more taxes as a percent of GDP than the US, so they must be doing something right.
In any case, their overall tax collections do not seem much out of line with other advanced economies.
https://en.wikipedia.org/wiki/List_of_countries_by_tax_revenue_as_percentage_of_GDP
My understanding is Greece's tax collection "problem" is rooted in a couple things. First, the government is widely viewed as corrupt and cronyist so sending money to it is wasteful. This is somewhat supported by the fact that roughly 25% of Greek workers are government workers. (And it turns out taxing the income of government workers to raise money for the government is a bit of a circular problem...) Second, Greece has a very low percentage of people who work for large evil corporations and get the Greek equivalent of W-2s. About 25% are self employed proprietors. These people are not necessarily "rich" as they may be shop owners or rent out a few rooms or run a gyro stand, but they are notoriously difficult to tax.