> A) Bitcoin is congested with transactions and takes hours to process some of them
Hours to process transactions sounds relatively good to me, considering international bank transfers take 3-5 business days. We're talking about a decentralized protocol performing better than a centralized one which has all the advantages on its side.
> B) Bitcoin fees are through the roof, it sometimes costs as much as 25% of the value of a transaction to send it
Bitcoin is definitely not suitable for small-value transactions (the fee does not depend on the amount sent). Here's a graph of median Bitcoin fees for the past year: https://bitinfocharts.com/comparison/bitcoin-median_transact...
> C) The upgrades to fix these problems are extremely slow - scaling hasn't been solved for years, because different parties keep fighting for control over the currency codebase and shooting down each others' attempts to upgrade it
This is a misrepresentation of the issue. The lack of a solution is not due to in-fightning, but that absence of an obvious "fix". The smaller the block size, and thus transaction throughput of Bitcoin, the more decentralized it is, because the more people can download and verify the blockchain using commodity hardware. It would be simple to increase throughput, but this would occur at the cost of increased centralization. At the moment, consensus seems to favor decentralization over increased throughput.
Bear in mind, that if hardware capabilities continue to increase at historic rates over the next 30 years, 1GB blocks will probably be doable, which will be roughly sufficient to support the world's population (with the addition of consumer-to-merchant clearing protocols). Some people think this is too slow, but I think the world needs at least 30 years to get used to a new monetary system anyway, so it can't happen any faster than this.
> D) Bitcoin is still, objectively, centralized. Almost all of the miners are based in industrial regions like China, and belong to a small monopoly of mining pools. All of the exchanges are centralized, and are well-known for losing clients' money.
The Bitcoin protocol is decentralized, because it does not define a central party. Saying Bitcoin is centralized because large mining firms exist is equivalent to saying that Git is centralized because of GitHub, or email is centralized because of GMail. Each individual miner (and exchange) is centralized, but on the whole they comprise a decentralized network of miners -- just like Gmail, Yahoo and Hotmail (together with all other email servers and providers) comprise a global, decentralized network.
That being said, Bitcoin is vulnerable to a constant 51% attack. It cannot withstand this (unless something fundamental changes about the protocol). So far, no one has bothered to carry out such an attack, but Bitcoin is vulnerable to this type of attack.
> E) Bitcoin addresses the technology perspective of sending money, but doesn't address any of the macroeconomic problems that arise from a deflationary, uncontrolled currency.
This is not fact, but opinion of Keynesian economists. The entire basis of Keynesian economics is this sentence.
For people interested in a much more meaningful explanation than Keynes' story of "things suddenly broke in 1929, and we had to ban gold to fix this", I recommend the following series of essays[1], which explain how the gold standard failed because it depended on a clearing market that was closed down at the start of WWI (in 1914) and kept closed at the end of the war (in 1918). This market cleared the "bill of exchange", which was a financial instrument that acted as a means of payment between retail merchants and producers of semi-finished goods, allowing the gold standard to scale as production became increasingly specialized. When bill of exchange clearing market in London was closed, producers were no longer able to pay each other using the bill of exchange, which caused demand for gold to surge (since it became the only means of payment between producers), causing deflation (an increase in the value of money is equivalent to a decrease in the price of goods).
[1] http://professorfekete.com/moneycredit.asp