1. Passive components distortion ? That should be really really really ****** components to have higher distortion than the drivers used (regardless of how low thd is in drivers). If you use components that bad, you will get bad measurements. That being said, you don't have to buy the expensive ones. Jantzen air coils (very fair prices at HiFicollective), Bennic/Wima 63V caps and regular 10W ceramic resistors will do. If you can't afford it, please stay away from loudspeaker building.
2. Active speakers are large chunk of the market ? True. But as always there are parameters that aren't included here. Sales of passive loudspeakers is down, no question about that. But number od passive loudspeakers goes up every year. With so many diy projects on the web, more and more people are making passive loudspeakers. Substantiated with good measurements and detailed planns, there is a pair for everyone of every shape, color and size. If you live in a house and have a living room larger than 40m2 i would really like to see what is the number of active loudspeakers that will play loud enough with dynamic range to spare and will cost under 10k€. For that kind of money you will buy a powerful amplifier and make (or someone will make it for you) loudspeakers large enough for the room, finished the way you want/like with money to spare.
3. Flatter frequency response and phase response in actives ? Well, sometimes yes if your actives are dsp powered. You can set the delay for woofer on axis to get perfect phase and frequency response. Trouble is that dsp isn't magic and you will get good phase response ONLY at that one axis. As soon you go off axis you can kiss you alignment good buy if you didn't do physical acoustic centers alignment at Z axis. Given that most of us are using some computers it is quite easy and inexpensive to apply some dsp action through pc for music on to passive speakers. That will get it at the level with best active speakers and costs nothing. And you don't need 6 dsp and amplifier channels of mediocre amp/preamp chips with high noise to correct the sound. Depending on the passive loudspeaker designer, a sound can benefit from biamping or not. I like to see separate amplifier for woofers if the impedance is complex - it could actually save some money for the main amp.
ONLY type of loudspeakers that make correct use of DSP and its abilities are SBIR loudspeakers. Those show true progress in loudspeaker design (Kii3, Bang&Olufsen Beolab 90, D&D 8C, Lexicon SL-1). There all the dsp hype is not hype - it is actually justified. Still, i don't like to see everything crammed up in loudspeaker cabinet. I really like what Axiom Audio does with their dsp powered loudspeakers. Drivers in the cabinets, electronics out. Putting electronics in speaker cabinet is always a compromise and it showed quite difficult/expensive to solve problems that arise because of that.
Passive speakers are here to stay for a long time and not because of inertia of some kind, but because they are still competitive. If they become obsolete, they will perish.