Huge drop in organic traffic after moving to NextJS

https://preview.redd.it/xybahmenaesd1.png?width=1477&format=png&auto=webp&s=f4a201e96b6e669843e97bc3cf48039ca25db7b0

I own Health website and In July this year (after many years on wordpress) i converted my site from wordpress to nextjs, but kept using wordpress headless on sub-domain.
i really satisfied with the site now. it works really good, load pages fast, really great. users stay on the site longer, and the user experince is much better.

but i have big issue with organic traffic, i notice there is graduall drop on traffic and it keep going down.
I did SEO optimizations of every relevant page on the site. i made non index for the sub-domain, new sitmaps, and so on.

I checked google console and i saw i have a lot of non indexed pages.. so pages like /tags i created it on nextjs, but there is ton of unrelvant pages of wordpress so im not sure if i need to do something about it.

Do you think google will figure this out on its own? i mean it will indexed it correctly eventually?

https://preview.redd.it/2vx6f9foaesd1.png?width=1407&format=png&auto=webp&s=54b433e93d25e9abe87be47748314185eaadbd88