I know the original post is about organs, so I'll say this first... Lowreys ARE easy to play, I think the primary target market is wealthy seniors! However, even the top-line Lowreys lack a mode where you can control the bass by playing specific inversions of the chord. You can play the pedals yourself if you have the skill. Or you can play the lower keyboard and I suppose the bass always follows the root.

Roland's late great Ateliers were competitive with Lowrey right to the end AND they had Roland's excellent Chord Intelligence with a separate toggle for bass inversion. Wersi OAX has 8 or 9 different chord modes(!) but based on a careful reading of the manual (haven't played one), there's a lot of redundancy and none of them are as convenient as Roland's system.

Circa 2000, Hammond offered an "easy play" organ with arranger features (the XE series.) It also adopted Roland's chord fingering system, and although it wasn't advertised, these instruments could play MSA and MSD styles ported on diskette from Roland's contemporary arrangers! I never got a chance to play one but these looked like nice instruments.

When the Harmony Central site with vintage synth reviews was still around, I spent a lot of time reading there. The highest-rated arrangers circa 2005 were the Korg i30 and Roland G1000. These models were actually rated higher than their replacements like the PA80, VA-series, and the then-new and slightly buggy G-70v1. The i30 was a big technological leap over the i3 and was frankly a lot more advanced than the G1000.

The i3 was a pioneering effort, but in a lot of ways the GEM (Generalmusic) WX-series also circa 1993 was just as advanced, with a more complete feature set. If I ever stumble across a working WX-expander module for a modest price, I'll MIDI it to my 1997 Yamaha QY-700 sequencer (with its chord-following "patterns") and have a combo that feature-wise probably exceeds any current arranger except the Pa5x!

Arranger technology is "mature" to put it mildly. Since 2007 or so, most evolution has been limited to improved sound quality and changes to i/o (i.e., touch screens replacing buttons, USB replacing diskettes, and limited tools for audio playback.) Ketron's EVM has no interface at all, just an HDMI port that works in conjunction with any generic touch screen! Maybe they're not selling many arrangers these days, because whatever is being sold isn't materially better than what folks already have! My $.02.