Naah, you just need to make bigger rockets . Up until very recently I've just been getting into the sun's orbit with a gravity assist from the Mun and taking it from there because I genuinely didn't realise that going straight from Kerbin orbit was so much more fuel efficient. Massive waste of fuel I know but I've fumbled my way across most of the planets and their moons like this so there's no reason why you cant too
Getting a gravity assist from the Mun should massively help in a interplanetary transfer if it's lined up. Works in real life afterall!
I imagine it's just a massive pain in the rear to line it up right in Kerbal!