For new investors, it is indeed profitable because they can buy good coins at low prices, but for old investors, they suffer a substantial loss. The advantage of a declining market for old investors is that they can accumulate coins or tokens, so the average price of their investment is low
I agree with you, like me who has been holding altcoin since 2017, hoping that if 2020 bullrun happens so I can sell all my altcoins and start investing in bitcoin even though I think it's a little late.
If you had that decision for long time then it is a perfect time you to withdraw it and start a new beginning in bitcoin and it is not that late because we knew that there is no late comers investing in bitcoin. now that the price is low you can accumulate as many as you want and you can earn much more by time so there a big different to have btc and potential altcoin. 2020 is upcoming and better to be ready.