Wow .. thank you so much to everyone who answered. I definitely learned a couple of new things from this thread. Thank you so much.
Yes, I agree I can just ignore them. But I noticed a couple of wads where the secrets do provide very good items, like a BFG or cell boxes or Berserk, etc, which might become helpful in some difficult levels, given that I'm not that much of a doom ninja right now and I do die a lot.
There are also wads that become very "puzzly" at times. And it's basically the same issue. You stop fragging and start wandering aimlessly.
But again I do agree that I should just ignore the secrets and just ignore the pain of the incomplete end screen.
I will definitely check the no secret wads list. Thank you very much. And I did play the first two levels of Sunder. I still have nightmares from that wad. But I will finish it.
Thank you so much all, you guys are awesome, I hope this thread helps other people who might have the same question as me.