Lulz how is this even a question. One is one of the biggest memes and songs of all times and the other is THE biggest song of all times and a huge pop bop.
Blinding Lights everyday until I die

Not the biggest song of all time, it helps that it came out in a terrible era for pop in terms of competition

I mean.... It has been in the top ten for 52 weeks, you're calling everything has been terrible for over a year?

First off since when it being in the top 10 for a year make it the biggest song ever more than than being #1 top 20 weeks in a row? Blinding Lights, Old Town Road and Despacito (also has a case for biggest song ever when including WW) all accomplished some amazing things in different ways

There is basically no way of telling whether Blinding Lights is a bigger hit than massive songs at the time like Smooth or I Will Always Love You or Yeah! or Every Breath You Take or whatever especially when Spotify is there now. How many weeks is Hey Ya in top 10 if there was Spotify? In my opinion there was also more bangers in the 80s and 90s. In 1999 when songs Smooth came out there was Baby One More Time, Genie in a Bottle, Livin da Vida Loca, Believe, No Scrubs, If You Had My Love, Bailamos, Unpretty, Heartbreaker, Say My Name, Bills Bills Bills, Wild Wild West, Every Morning, Steal My Sunshine, All Star, My Name is, Larger than Life, etc. and was still in top 10 30 weeks and #1 12 weeks. I wish there was that many catchy songs at once nowadays.

And yet both Old Town Road and Blinding Lights came in the same year and were released just a few months apart. So it's just incorrect to use the argument when comparing these two songs.