Bitcoin is going 9yrs old, so far no alts surpasses Bitcoin. For 9yrs it remains the king. While Bitcoin is going down, no alts remains strong. All alts are crashing too. This is the best indication that Bitcoin has no replacement.
All this is changeable. It should be noted that altcoyins have been developing only a few years, in fact since 2015, after the appearance of ethereum. They have achieved very good results and have already far surpassed bitcoin. Bitcoin while holding on to the leadership on the former authority and popularity. The only way to maintain leadership is to continually improve and maintain competitiveness among other crypto-currencies. This is the law of the market. Bitcoin is still very far behind.