[Question] fake keyword competition

hi all.

im trying to rank a page with single post for specific long tail keyword(8 words with 1500 avg searches), when i checked the top ten results in google search i found the top page are high authority sites with PA>50 DA>50, but the long keyword didnt exist in any page's title or url maybe 3~4 words exists and not in order. im really confused cant decide if it is a hard or weak competition as example for my keyword you can check this one "healthy diet plan to lose weight fast" it has a similar criteria.

thanks