If you are a normal person with a working life and salary, you should definitely go for the dca method. Like you said, bitcoin can be life changing if you already have a lot of money to invest in bitcoin since bitcoin is just too expensive.
But this should not discourage people from investing in bitcoin. I would rather slowly but constantly invest in bitcoin than dump a huge amount of money into an altcoin I have no guarantee of making profits.
Priority matters my friend. I'm not sure the kind of profit an altcoin can give you Bitcoin will be able to give you such in anytime soon. I mean, will be a quick fix to make 5x on good working altcoins than for you to make that from Bitcoin, that's like making Bitcoin cross above $200k on the market but altcoin can make this happen under some days just that the risk in altcoins are not worth it sometimes but if you invest in good altcoins, you will only worry less about altcoins.
Bitcoin to me right now is capital requirement, you can't get enjoy the versatility in altcoin and Bitcoin. The money you need to make more money in Bitcoin is quite large, though if I personally has the money, I will pick Bitcoin before any other altcoins because it tend to give more yield on the bigger side if you have the power to hold onto 1 full BTC or even more.
What you said is true, for me I see altcoin as a short-term investment, no matter how good altcoins pump during bull run they can never be compared with Bitcoin, lets not forget that there is every possibility that highly speculative coin has the tendency of pumping and dumping fast, we all know that altcoins are highly speculative as such investing in altcoin requires a high level of carefulness, as an investor, risk management should be your utmost concern, I don't think that it will be wise to take uncalculated risk because of the feeling that a particular coin may pump due to the hype given to it by the so called influencers, before making some move due to this fact, we should know that influencers are paid for their work done and whatever comes after does not really matter to them.
Know doubt altcoin can make people rich within a short intervals but the problem is knowing the particularly one that can do that, my major problem with altcoin is that no matter how good you think you know crypto, you can not invest in altcoin and feel free, there must be a little fear because of the unforseen circumstance.
Bitcoin is one in a million because it has the ability to make your money more valuable in the future but pump and dump coins can not give you such futuristic concept.