Take delivery dates and stock availability with a grain salt, online retailers ship thousands of stuff daily.
Use common sense, not everything will go smoothly. Ranting about those small issues is just irrational.

Ultimately, there's always a risk of complications buying online .. so before you click buy, double-check that the vendor is reliable by going through its collection of items offered.
You can detect dodgy vendors from their pricing or review trends of their other products. Vendor age in Lazada is also another indicator, be vigilant with younger vendors.

Take for example a few months back, the case of Nokia 3310. The whole Lazada was flooded with fake Nokia 3310s, selling significantly under the retail price.
I've no doubt that people have been scammed to buy a fakes, the price was too good to be true. Whose fault was it?

Both, but primarily the buyer themselves.

You cannot expect Lazada to police their products and expect 100% compliance for genuine items. It just doesn't happen in reality, nor practical to implement.
If they get a commission for every sale, regardless whether the product is genuine or not, the issue of fakes proliferation will usually take a back seat.

You as a buyer, with god given intelligence, should exercise due diligence to minimize the risks - in the above case, research about how to identify fake Nokia 3310.
Nowadays, information is at your fingertips. Use it. You won't completely eliminate the risk but at least you've avoided the simple traps.

P.S. For the moment, my purchases from Lazada have been all positive after doing some homework.
I also refrain from purchasing huge/heavy/bulky items through post and rather get them in normal stores, to remove risk of complications during delivery.

Also, I prefer the 7-Eleven MOL payment scheme over direct debit/CC or Maybank2U. Just pay at any 7-Eleven store.
It's easily traceable, minimal hassles (lots of stores near my place) and removes any possible connectivity issues during the payment process.

If Lazada offers the moon (yes, that one shining in the sky at night) for RM1500, will you happily click buy it without any thoughts?