Yeh Lemmy is unfortunately going to have a very hard time growing to be even 10% the size of reddit. The whole decentralized thing is good in theory, but not great in reality. As you said, now entire communities can be deleted at any time, and as it gets more popular it will cost more people more money and with no way to make money to cover ever increasing server cots other than donations. Also there’s not going to be any guaranteed performance level across instances because they’re not all hosted on the same hardware in the same locations.
I want reddit to crash and burn at this stage, but unfortunately I can’t see it happening. Lemmy will crash and burn if it were to actually become a reddit competitor. I’ve already seen people asking for registrations to be turned off because most servers can’t even handle the minimal number of users they now have! That’s not how you grow a website/community lol.
Also as you mentioned, mods is a big worry. Mods are the main problem with reddit IMO, along with the admins. They push their ideologies, they shadow delete and ban people that they don’t like/agree with, and they just wield the banhammer without warning and without consequence. Are the mods here going to be the same? Many of them will literally be the same people that were mods on reddit, so that’s not a good start.