Bitcoin is indeed more able to provide certainty of profit for long-term investments but altcoins can be used as a way to increase our number of bitcoins if one of the altcoins we choose turns out to be pumpable by someone else and we benefit from this action, only that is too speculative because like what you say is too centralized so that developers or anyone who has a large portion of holding the altcoin will have the opportunity not only to increase the price but also to drop it to create panic so that we are very likely to sell at a loss, so Bitcoin is better for those who like calm and who prefer it for the long term.