Bear market will not be like the past history as crypto is getting popular day by day and investors are increasing. So we can say bear market is the best time to build portfolio and also it will not go too dip like 2018 if we don't face any bad news.
However, it is just in the bear market that it is difficult to understand which Altcoin will have the largest APY% at the next steer. I would not risk forming my portfolio precisely during the decline in the market, especially as happened in the past. It is better to start creating a portfolio just at the early stage of the bullish trend. But how to correctly recognize this moment is the question and ability of a crypto expert.