Gen 5 and 6 missed some Pokémon forms, like Deerling Winter, Sawbuck Winter and Autum and even some Megas! I know Gen 5 didn't last long for TCG, but Gen 6 should have at least included the Megas, since it: 1. ran longer and 2. had less new Pokémon.
Other forms missing are:
Arceus Fairy and Dragon
Individual Cosplay Pikachu cards
Genesect Drives
Majority of Vivillon Patterns
I know a lot of those forms are minor, but back in Gen 2 and 3 they'd include all Unown forms, all Burmy and Wormadam forms and all of Castforms forms.
At least Gen 7 feels more inclusive and included all Alola forms, Ash Cap Pikachu as individual cards and the battleable Zygarde forms. Though they're still missing Minior and Sylvally forms.
Other forms missing are:
Arceus Fairy and Dragon
Individual Cosplay Pikachu cards
Genesect Drives
Majority of Vivillon Patterns
I know a lot of those forms are minor, but back in Gen 2 and 3 they'd include all Unown forms, all Burmy and Wormadam forms and all of Castforms forms.
At least Gen 7 feels more inclusive and included all Alola forms, Ash Cap Pikachu as individual cards and the battleable Zygarde forms. Though they're still missing Minior and Sylvally forms.