But for those who are looking beyond just making a quick buck - yup we should avoid trusting any 3rd parties as far as possible.
Who are the guys you're taking about?

They went extinct or at least extinct in the wild and unable to reproduce during the '19 bull run!
The whole thing of "not your keys not your coins" which probably I'm going to take to the grave is just a saying now, everyone claps , agrees, says it's so much better and then 99% of them park their coins at Binance!
And before anyone says about the "dwindling" coins in exchange's cold wallets, nobody has yet been able to tag alll of neither Coinbase Bitgo accounts, nor MicroStrategy wallets nor the coins that Salvador supposedly has!
It takes away the risk of them losing btc due to hacks, losing private keys or messing something up.
Cough cough... mattress cash vs banks!

I don't see a disadvantage of having a management fee because you will only pay it yearly. It just only a little amount of funds compare to your potential annual profit.
Paying something for a thing you could do yourself just for the promise that your coins actual exist is not a drawback?