Why are adcs so weak in this meta ( currently ) and what buffs or changes do you suggest ?

I don't think it's because ADCs are weak. I think it's because bot tower sucks and because damage has increased across the board.

Personally I believe it's because people realized that it's best to shut down the enemy bot laner as early as possible do they don't have to deal with them late game. Combined with the weakest tower and dragon, bot lane has effectively become a treasure trove of objectives. Which leads to a lot of increased pressure early game.

For a late game class like Marksmen, this is an absolute nightmare because they are at their weakest. I blame it on the jungle exp and gold. Forcing people to gank more only helps early ganking champions like Lee and Vi.

I honestly have to laugh hard at the "ADC's are weak" posts. Try winning games without an ADC on a consistent basis. This Ziggs phase will end since he is stomping mid as well, so they will nerf him and he will be gone from bot. ADC marksmen are the only required class in the game.

they just need to rework crit and adc itemization.

The sad thing is, you can't even fix this by lane swapping, because if you do, your stupidly weak paper bag of a tower is going to get 3 man'd by the enemy bot lane and jungler, giving them free gold, and completely screwing over the solo laner