Now my question is, is it good for my future that I have sold my altcoins and invested in bitcoins?
Let's say usually, at first, when you're new to this world you buy several altcoins, then you realize many of them are pointless and it's better to focus on BTC, so I would say you made the right choice. The only altcoins I really like are ETH and BNB, those have a great potential and it's worth having some, especially ETH in the short term it may even outperform BTC.
Perhaps that's what the OP realized, and I think for those who are in the crypto market for less than 4 years, they really think that altcoins is the best because of the perceived returns and how it was exaggerate by the media and other crypto influncers.
I would agree that there are solid altcoins like you mentioned, but majority here are into Bitcoin and most of their portfolio might have been shift to
BTC already and then become a long term investors and a HODLer.