"Ice and Bug need buffs" is a common opinion, but "Rock needs buffs" is an interesting one. Rock is one of the better offensive types, Rock Slide is everywhere in Doubles, Stone Edge is both hated and feared, and Sandstorm increases their Sp. Def.
I guess its weaknesses (Fighting, Grass, Ground, and Water) are all inconvenient, but "needs buffs" is otherwise kinda vague. Increase the distribution of Power Gem, maybe?
In-game, I don't think there are any truly weak starters, let alone recently. Meganium struggles in Johto, sure, but it's far from the worst Pokémon in the region, and IIRC it's still usable in a playthrough. The Johto trio is also by far the most imbalanced in-game to my knowledge, Chikorita is clearly worse than Cyndaquil and Totodile.
What I would like to see for Starters is similar power levels within a trio. Yet even today, we got stuff like Incineroar being a lot better in Doubles than the two other Alolan starters. Competitively, it's all over the place, especially since Generation VI I feel like.
And not let me talk about publicity... *cough*Charizard*cough*