No proper horn is shouty. Cheap undersized poorly designed horns over a ported box can have issues since midrange is so much more efficient most compromised to make them smaller cheaper. A proper horn is fully front horn loaded to at least 100hz not many like this exist that audiophiles would buy so they opt for small poorly designed horns then go online saying that all horns shout or some such BS.
Indeed; all things more or less equal the bigger the midrange horn the less it sounds like a horn (and almost akin to a large panel speaker), although in the lowest octaves horn size - i.e.: length, overall volume and proper/corresponding mouth area - mainly dictates frequency extension and SPL, and so is set according to the desired parameters here. That is to say: in the bass department there's no cheating out with bass horns with regard to the size required in relation to extension (and SPL) needed, although variants of bass horns, like tapped horns, can further maximize the output for a given volume/horn path length in summing the output at the mouth of both the front and back wave of the driver, where a front loaded horn can only take advantage of the driver's front wave.
What's missed with smaller midrange horns more technically is dispersion control in the lower end of their frequency range. Some of them may be able to be high-passed at and sound rather well down to ~500Hz, but dispersion control has flown out the window an octave or more above. Maintaining dispersive pattern (preferably similar to the driver segment covering the range below it) and control at the cross-over that's offered with the big midrange horns isn't trivial sonically speaking. As proposed by you a proper designed and sized midrange horn doesn't sound shouty, as in at all, or what people typically associate with bad sounding horns. Smaller midrange horns, even though they're well designed, generally sound more aimed-at-the-listener, less enveloping and more agitated vs. a larger midrange horn covering the same frequency span, that by comparison sounds more relaxed, physically realistic, dynamic and with a better fill of the sound throughout the listening room. The smaller horn may impress at first with its "lively" imprinting, but it really stands more in the way of the music and ultimately can't hold a candle next to their larger, well designed brethren.
