I mostly use exchanges since i could not download the hole blockchain
2.(i gave up after 10 days trying to sync the Bitcoinclient. i achieved only 46% with a 50mbit highspeed ISP !)
3. the fees are too damn high like overpriced fiat bank services
4. even if problem 1 would not exist its still damn slow in nature. But with with that fee-issue which exists since 2013 or longer
Bitcoin is a fail for me for these 4 reasons.
You do not need to run a full node in order to use bitcoin. There are light wallets that you can use that basically have all the functions and the security that you need. The long transaction confirmation and high fees goes hand in hand and should be solved by segwit or whatever solution the core devs are proposing but the miners are taking their sweet time in electing it. Bitcoin is not perfect but I do not think there is an altcoin out there ready to replace bitcoin, YET.
Write me here or to PM