It can be difficult to say for sure what any person should do, yet if a person invests similar amounts of value on a regular basis (such as weekly) for 4 years straight, then their average cost per BTC will be right around the 200-WMA - and historically, an overwhelming majority of times, the BTC spot price is at least 25% higher than the 200-WMA.
Of course, there are no guarantees, so any of us who might be attempting to think and act rationally, may well consider that it would be good to invest into bitcoin for a whole 4 -6 years or more and then perhaps to reassess after that. Surely if we are able to frontload our bitcoin investment, then we may well have differing results, yet there are not too many normal people who are easily able to frontload their investment into bitcoin. And, yeah, for sure, each person has to decide for themselves whether and if so how to invest into bitcoin.
People, especially newbies, don't do much research or apply methods like DCA so that they can have a better buying average if they are investing a similar amount every month or week, etc. What they do is they put together some money and then wait for the perfect time to make an entry, and for most people, the perfect time is when Bitcoin falls down to $30k or below because they believe that is the only way they are going to get profits from it.Of course, there are no guarantees, so any of us who might be attempting to think and act rationally, may well consider that it would be good to invest into bitcoin for a whole 4 -6 years or more and then perhaps to reassess after that. Surely if we are able to frontload our bitcoin investment, then we may well have differing results, yet there are not too many normal people who are easily able to frontload their investment into bitcoin. And, yeah, for sure, each person has to decide for themselves whether and if so how to invest into bitcoin.
Now, when they are waiting for that perfect moment and not buying when Bitcoin is around $90k or something, if Bitcoin goes higher, let's say above $120k or something, they might regret it, but they will still wait for it to drop. This makes people lose so much time and opportunities because their minds are only stuck at that perfect moment in which they will cash and make an entry in the market so that they can get more profits over time.
I agree that a lot of people have a tendency to wait or to time their entry point into bitcoin, which is part of the reason why so many of us longer term bitcoiners continue to suggest that one of the best things for any no coiner to do is to just get started, and the same thing is true with low coiners who are fucking around waiting for better prices, it tends to be way better for the low coiners to just continue to buy, and to buy regularly, persistently, and consistently for 4-10 years or longer. Sure if they are able to front load their BTC investment, then they might not need to continue to buy for 4-10 years or longer, yet an overwhelming majority of normal people are not able to front load their bitcoin investment, so it is likely best for them to just continue to focus on regular, persistent, consistent and perhaps even aggressive buying of bitcoin for 4-10 years or longer and not to worry about price.
After several years of buying bitcoin, then newbies are likely going to become more and more informed about their own situation and their bitcoin stash size may well also help to inform them in regards to the extent to which they might need to adapt their BTC accumulation approach in accordance with their 9 individual factors.
In the future, people will only transact using CBDCs (aka Digital Fiat) and crypto (BTC, ETH, LTC, etc.). That's when we can say it's late to get into Bitcoin. Until then, I'd suggest you keep buying and "hodling" BTC while it's still cheap. Untold riches awaits to those who wait. Just my two sats. 
Why does it matter if people are starting to transact with CBDCs and various crypto such as BTC, ETH, LTC? That makes no difference.
If the future comes and a person is still a no coiner or a low coiner, then they still need to get started buying BTC, for their own good.
The BTC price also does not matter. If the BTC price is $1 million, and the person does not have any BTC, then they are going to have to buy it at $1 million.. Whether that is in this cycle or next cycle or at some other point in the future.
Of course, we could have a day, 10-15 years down the road, and bitcoin could have prices bouncing between $20 million and $50 million per coin. Are you coin to tell them that they are too late to buy bitcoin, and they need to buy some inferior currency or asset? If they are a low coiner and/or no coiner at that time, then they are going to need to buy their BTC at the then going prices.