This is based on personal observation and studies of the altcoin market of a period of 2017/22
Altcoins are said to be the alternative cryptocurrency aside from Bitcoin and many of the altcoins are decentralized and also centralized, unlike Bitcoin which is highly decentralized and out of the control of anyone be it the developer or government Bitcoin has a total circulating supply. But Altcoin is developed by individuals e.g Vitalik Buterin Ethereum developer and teams members who are known in the society and the source codes of the coin can easily be updated which have made them not to have a static circulating which is has been the major reason why the altcoin market is hard to speculate because it circulating supply can easily be tempered more coin being minted at will which will render speculators analysis inaccurate in most cases.
I think you described the altcoins market too generally. Of course, there are many similar coins, but there are many that are completely different from each other. Of course, there are those that are constantly developing and there are some changes in the code, but the point is that they should be constantly improved.
I think I can agree with you that long-term speculation is more difficult on altcoins due to the human factor - we are just not sure when any developer will want to abandon project, for example.