a) Is Monero as suited for it's stated goal of private transactions as it claims
b) Is it better suited to this goal than using properly coinjoined btc over Tor
c) Is Monero actually decentralized to a decent degree
d) Why Monero will fail in the long run
Monero is the best privacy coin. You can see the explanation and guide of admin.
[Guide] Decent mixing methods.
Nobody is able to trace Monero transactions and successfully break its privacy and anonymity.
Whether the Monero network decentralized or not and how decentralized it is? It is decentralized but is not a biggest altcoin network that belongs to Ethereum network.
Monero falls in long term because governments force exchanges to delist it and there are FUD that Monero transactions can be broken down, and its anonymous transactions will be broken soon.