Whis apparently says Goku and Vegeta working together could defeat Beerus. And Freeza in his non-golden form was stronger than SSJ Gohan(and presumably Piccolo) but I have no idea what that entails and base Goku could fight him.
^ Yeah, the moral of RoF was teamwork between Goku/Vegeta. When they stopped working as a team, the earth paid the price(short-lived as it was.)
Base Goku was able to fight him because all of his power is now accessible in his base level... Which, ironically enough, is the exact same thing Elder Kaioshin's unlock allowed Shin Gohan to do years prior. Surprised it took Goku so long to hop on that bandwagon.
And Gohan opted to hop off that bandwagon since he is still going SSJ. I mean he shouldn't need to(Shin Gohan could do it but it was pointless) but he has. And he thinks Freeza is way out of his league. Imagine if he was as strong as he fought Super Buu? Jesus.
Toriyama went from wanking the bejesus of of Gohan any time he could(he was originally going to have Gohan save the day in the Buu saga as well, until he was shut down by studio execs and forced to have Goku be the one to destroy Buu), to literally shitting on Gohan for no logical reason.
It may as well be called "The Goku and Vegeta Show" these days.
Well I actually rather like how Toriyama handled Gohan in the Buu Saga but that's because I thought he was poking holes in the idea that Gohan would be a perfect successor to Goku(doesn't train enough, often holds back due to fear, and didn't end Buu quick enough).
But yeah the focus on Goku and Vegeta is annoying. Toriyama was at least nice enough to continue giving Tien stuff to do even when he was outclassed, and he also gave Roshi a moment which was awesome. But the fact that it has to be those two in particular who are always head and shoulders above the rest gets a bit irritating.
Dragonball has never been the best written thing but the shift from Tien and Yamcha to Piccolo and Vegeta worked. Gohan was a pretty good character to bring in as the next Goku but like you said Toriyama has no interest in him. The kids are kept around to be funny and cute. Piccolo is too outclassed at this point to matter in a fight so we're left with just the two rivals.