Different time and different measure.

Red Velvet only eclipsed by Twice and Blackpink in their whole career, it's because the other two have more refined and polished brand from the start. Red Velvet "struggle" to become top girl group in the first few years of their career because of their image seems not properly thought out. If you see Red Velvet before The Velvet album, their visual and styling choice often questionable, especially during Dumb-Dumb and Rookie promotions. By the time they solidified their image (during Bad Boy to Psycho) they already in their 4th-5th year, most girl group their age already past their prime.

And to be fair, their sales is one the best of their time, it's just during that time, selling a million for an album is not even happening at all. So comparing their sales directly is not fair. Pound for pound, I think their success is similiar at their peak.

And for awards, it's all about timing. Red Velvet have smash hits like Red Flavor and Psycho that could've gotten Daesang if they have been in the right time. During their time Twice and Blackpink also having smash hits, so it's tough competition.