There's a lot of loopholes you could plausibly escape through. For one: you could use hybrid atmosphere-breathing engines to get most of the way to low orbit. (Using ambient atmosphere as a reaction mass circumvents the rocket equation). From low orbit, you can switch to electric thrusters with Isp much higher than the engines considered here: it's no longer necessary to have a thrust/weight ratio greater than unity.

A hydrogen planet would be particularly easy, since the light molecules would maximize Isp for a (non-combustion) thermal engine. A nuclear scramjet on a Hycaean world would have some truly impressive performance.