I believe that Nightwave was not an attempt to better the game experience for the players. It was not, as was touted, a way to remove the 'missing out' from something that an Alert offered for a limited time. If that was the motivation, there are many easy ways to address it. Extend the Alert duration for desirable rewards is one way.
Add the Nightwave system to the existing Alert system is another way. If you want to grind away at random tasks that may or may not interest you so that you can eventually get exactly the thing you wanted, Nightwave gives you a guarantee. If they had kept the Alert system but added Nightwave, maybe you will get lucky and be available to play when it's part of the Alert system rewards. You think they have any problem with making people get lucky? Try cracking open some relics, once you are lucky enough to get the relic you need. Then get an Ivara warframe. And an Ash. And most of them.
No, Nightwave was not motivated by a desire to improve the game for players. It was motivated by a desire to control the economy of items that can be purchased for platinum. Under Alerts, if you played more, you got more. There was no effective hard cap of 'Wolf creds' that limited you to 1 potato per week at best and that only if you got nothing else.
Nightwave does not exist to make the game better. It exists to make the game more profitable. They will never return to the Alert system, because it interferes with their desired monetization of the game. Warframe is free to play, and I believe that it has the least intrusive monetization system of any free to play game. Nevertheless, I would have preferred more honesty in their disclosure of motivation.
If Nightwave was meant to fix the shortcomings of the Alert system from a player's point of view, it would have supplemented Alerts and not replaced them. But it's not meant to do that. It's meant to provide incentive to the people who play the game the most to buy platinum.