Again, the problem is trying to use DBS-era Gotenks as a measuring stick. As I've just shown you, his power in DBS was portrayed vastly different than how it was originally portrayed in Z.
Like I said earlier: per DBS, the BoG arc is set a mere 6 months after the Boo saga, yet SSJ3 Goku and SSJ2 Vegeta(rage-boost) are regarded by Beerus as substantially more powerful than anyone else he'd fought... And he fought Gotenks(SSJ3 Gotenks in the manga), as well as Mystic Gohan.
ie. at the start of DBS, SSJ3 Goku ~ SSJ2 RB Vegeta > Mystic Gohan > Gotenks.
...And there is absolutely NO reason to believe the powers of Goku and Vegeta had improved much(if at all) in the 6 months between the Boo arc and BoG. Moreover, when Beerus stated that base Goku was weaker than Freeza, no one disagreed with him, and we were given absolutely no reason to assume he was wrong. That is simply the level of power Goku was intended to be operating at when DBS/BoG first began.
Fact is, Gohan and Gotenks were clearly no longer intended to be dozens of times more powerful than Goku and Vegeta in DBS. Toriyama has obviously changed his mind about the younger generation supplanting the older generation -- it's the "Goku & Vegeta Show" now, and their kids are little more than comedic relief on a good day.