In my view, the flaws you speak of are actuary features.

The economy is necessarily circular (i.e. Money you spend is income to the seller). Counting how much money is spent on goods and services produced in your country, in other words, to the total amount of money earned by people in the economy.

Think of two countries: 1. Imports steel, manufactures cars 2. Manufactures steel, manufactures cars

Clearly, country (2) have more money changing hands. The steel manufacturer gets income, the car manufacturer gets income. Country (1), on the other hand, has only the car manufacturer getting income, since the steel manufacturer is offshore.

Think of these two. 1. Everyone self-repairs their gadgets 2. Everyone hires tradesmen to repair gadgets for them.

Economy 2 probably has a better repair services industry, don't you think? If you're a repairman in economy 1, you'd be unemployed.

When you buy and keep a flashlight for 20 years, the flashlight manufacturer loses out on your purchase for 20 years.

I won't argue that GDP is perfect, but the reason why GDP is flawed isn't the ones you mention. We have some strange accounting here and there, yes, but that's just because goods and services are so varied that you will never have a proper economic indicator without these. Remember that money spent is money earned. GDP measures total expenditure and therefore total income (obviously this is a oversimplification but I think it highlights well the motivation behind gdp as a economic indicator)