You have been registered on the forum for less than 2 years. So have you been accumulating bitcoin for that amount of time or longer?
I have a hard time figuring out how most people would be able to accumulate enough BTC in less than 2 years, especially with the BTC price pretty much going up the whole time.
Sorry for the late reply, I've been starting DCA for about a year and of course I'm collecting as much as I can, at that time since the BTC price was more or less under $20k. At that time I realized and read on this forum that the DCA system is one of the best ways to collect BTC.
It's true that I haven't collected a lot of BTC, but I realize that of course it's never too late to start and stay enthusiastic and do DCA regularly, but honestly I feel happy, even though at the moment I haven't collected much BTC, at least I've succeeded in doing DCA and this really makes me happy. I am happy.

Indeed, it doesn't feel easy when you look at the price of BTC because the price continues to rise, but what is certain is that because I put in money that I was ready to lose, which was put into buying BTC, of course it felt very light and definitely without a burden.
Being able to consistently run DCA for a duration of 1 year is indeed quite an extraordinary achievement. Because some people definitely have difficulty consistently doing DCA on bitcoin. But don't forget, you must have a goal or time duration for the bitcoin investment you are currently making. Whether it's for your retirement, or for your children, or for other things. Because with such careful planning, it will usually make us more motivated to make more money, so that we can invest more of our discretionary income into Bitcoin.
Apart from that, talking about your assumption which says that one day (in the future) people will fully invest in Bitcoin rather than Altcoins. This is quite reasonable. But in my personal opinion, even though bitcoin is the number one crypto asset and the safest to invest in, especially in the crypto realm. But I think it will be a bit difficult to get everyone involved in the crypto world to abandon Altcoins completely. Perhaps the most realistic thing is that people who are involved in the crypto world, it is very likely that the majority will invest in bitcoin. But they are also likely to continue trading in Altcoins. I think it's very likely something like that will happen in the future. Because it cannot be denied, many people who are involved in the crypto world will definitely still be tempted by Altcoins in the future. Because they hope they can get thousands of percent profit from the altcoins they buy. But this is very risky, so I personally would be better off investing my money in Bitcoin, rather than in Altcoins.
First of all I have learnt from this thread that it is not good to use the word "crypto" in describing Bitcoin and the other coins and the reason they gave was that Bitcoin is unique and as the pioneer creation, its name should be retained to avoid contradictions. Remember that many people are perpetrating scams and creating many bad assets, so calling everything crypto including Bitcoin may suggest to people that Bitcoin is just like some of those other things that make people lose money.
Furthermore, the temptation to invest in altcoins like you called them, will always be there for those who are not informed and who does not know that Bitcoin is all they need to succeed without taking too much risk with their money. But I'm sure a lot of people are getting wiser now, not 100% but great proportion of people are chosing Bitcoin and many will still do that as time goes on. It is getting to one year since I joined this forum and I have read from here and also seen in the news of some Bitcoin blogs and magazines how notable coins that people thought were reliable failed and made people lose money. The one I can remember very well is Luna (Terra) that crashed and sent some people to poverty, people who put all their life savings in it. I have also read about others too but for the sake of going straight to the point, I will not mention others but I believe you understand what I am saying which is simply to retain the word "Bitcoin" which is better and safer to invest in like you already confirmed.
My understanding of how important it is to invest only in Bitcoin is what has made me to start buying small whenever I have money I don't have urgent need of. I started around August last year after spending about 7 months in the forum and since that I have not sold any of my Bitcoin because I have plans of holding them for a long time. I will be sincere with you, I was actually tempted to sell at some point but thank God for this forum and the people here who I see are not in a hurry to sell. I usually admire people who have Bitcoin so I said to myself that I will also have this Bitcoin too and treasure them so well.