There's plenty of time to criticize, improve and push the BJP later on - but the real priority right now is to wipe out the blatantly antinational and anti-Hindu opposition. They're a far bigger, and existential threat to India and Hindus than the "mediocre" performance of BJP. But there are people literally complaining about Modi and BJP, talking about NOTA or "teaching BJP a lesson" etc. That's plain suicidal.
The opposition simply cannot be allowed to exist in its current form. Wipe them out, and allow a fresh opposition which isn't as blatantly corrupt antinational and anti-Hindu as the current one. There is room for a liberal, left of center opposition; there's room for centrist parties, and there's even room for right of center parties that don't agree with BJP on everything - but all of them must be pro-Indian and secular in the real sense of the word (even Congress under the right leader can work - like Amarinder in Punjab, who I prefer over SAD). Then they're all welcome to compete for power, and in those circumstances, I don't really care what happens to BJP.
But right now, it is beyond crucial, and an absolute priority to root out Lalu-Mulayam-Mayawati-Gandhi-Pawar-Mamata-Kejriwal types.