Does it mean that what was defined earlier for the average block size doesn’t matter anymore and would not matter in the future also?
The manner in which that limit was defined is extremely important; through a softfork. An old client wouldn't see a 4MB block. The block size limit is, still, the same. What SegWit did, was to segregate the digital signature and place it in a separate, extended block, while retaining the validity of the transaction as old clients would see it. The size limit increase wasn't arbitrary. If we find another option to redo that in the future, then good. It'll be down to the user's choice to opt-in or out the softfork; they'll still remain part of the Bitcoin network, enforcing the old rules as much as it's practically possible. But as I see it, the proposed way is through a hardfork, essentially tinkering with the block size limit, arbitrarily one could say.
silly me I also look at the mempool.space and found that the block can reach more than 1 MB and just by looking at it easily get 2 MB of data can you guys explain to me 
