do you have the opinion that lone investors who are not members of any kind of forum or community about bitcoins or cryptocurrency can still be very successful investors?
Yes.
After all, Bitcointalk isn't the only source of knowledge when it comes to cryptocurrencies. I mean there are many websites out there that can give as much information as Bitcointalk can give (or even more). Though I don't personally know any investor that isn't registered here (I don't know many people around me that's invested into crypto), I still believe that there are some who became successful investors even though they aren't joining any forum.
There are many ways for an investor to gain knowledge. There are many social media platforms out there that gives information as well. Well, when there's many information, there's also many of misinformation out there so just be careful.
Truth of the matter is, it is going to be a little bit difficult to have investors who do not belong to forums or groups or even small communities, you know, where they discuss about the market trends and the upturns and downturns of the trades that are going on in Bitcoin, and how the Bitcoin market is progressing.
I feel like being a lone investor in this kind of digital community is going to be a little bit difficult because there would not be a reason why you shouldn't belong to one. Since your intention is to gain good knowledge from other platforms, especially real-time information about what the market entails at that particular time, you want to be up to date with how the Bitcoin resources are moving and where and when you should put your investment or withdraw investment from. In that regard, you also want to get experience online from real experiences of other people who are also investing at a particular point in time.
It is good to mention categorically clear that being in a forum or community is not a criterion for becoming an investor. If you have the right information at the right time, you can always make the right investment plans.
Bitcointalk may not be the only platform where you would get that knowledge or the only forum where you can meet and connect with people. There are many other forums like, you mentioned, however, Bitcoin is one platform where you would get to communicate with people directly and even join trades and conversations that would help to make the right choices and take the right decisions as far as Bitcoin investment is concerned. But there are other platforms, even on social media, that you can go into to learn about Bitcoin. However, I believe Bitcointalk accommodates more real people and a diverse set of users of Bitcoin, active traders, and investors, whether they're into lump sum investment or DCA approach to investment.