I get what you're saying, maybe it was just an exaggeration of power to hype Broly up and it makes sense via powerscaling. You raise a very interesting point actually so I've decided to do a bit of maths.
Vegeta when he fought Goku had a power level of 18,000 and he was going to destroy the earth before Goku stopped him. Now it obviously doesn't take someone with such a high power level to destroy the Earth seeing as Master Roshi was able to destroy the moon with a power level of 200 and Piccolo was able to destroy the moon with ease with a power level of around about 3000. (Estimates take from the official Daizenshuu guides). If we take the minimum amount of power 200 (which is Roshi's) to destroy the moon and x49(How many times the Earth is bigger than the Moon) we get to 9,800.
So it would take a power level of around about 9,800, probably less seeing as Master Roshi didn't really strain everything into destroying the moon, to destroy the Earth. Once again though this is assuming everything is scaled.
Well when Goku went SSJ for the first time his power level was 150,000,000. Which means he could destroy 15306 Earths. The official Kazentai battle book states that with every SSJ transformation the Sayain's power is doubled. This I assume excludes all the training the Sayain does after achieving a transformation so would probably give a very baseline figure. Either way this means that when Goku went SSJ3 his power level would've been 600,000,000 as a minimum (Probably a lot higher than this). That would mean he could destroy 61,224 Earths.
LSSJ Broly on the other hand was stated to have a power level of 1,400,000,000 which means he could destroy 142,857 Earths.
Now for some size scales. Jupiter the largest planet in a solar system is around about 1317 times the volume of the Earth, so Jupiter would get crapped on by anyone above SS level. The Sun however is massive and it's volume is 1,300,000 that of the Earth.
Hopefully that little bit of quick maths can come in help to someone in the future and hopefully it was a somewhat interesting read lol.