I love their designs and Synthesis is an incredibly useful tool in restrictive itemless runs, but just look at the gyms:
Falkner (Flying)
>weak defensively, resisted offensively
Bugsy (Bug)
>weak defensively, resisted offensively
Whitney (Normal)
>neutral defensively (but resists Rollout), neutral offensively
Morty (Ghost/Poison)
>neutral defensively (move wise), resisted offensively
Chuck (Fighting)
>neutral defensively, neutral offensively (but effective against Poliwrath)
Jasmine (Steel)
>neutral defensively, resisted offensively
Pryce (Ice)
>weak defensively, neutral offensively (thanks to secondary typings)
Clair (Dragon)
>neutral defensively, resisted offensively
The Elite Four is just as bad with the constant Poison or Flying mons. This coupled with Meganium's absolutely horrendous coverage (literally just Grass and Normal) and the plethora of alternative grass types completely seals the deal as worst starter.