Not so. There have been significant advances in driver design and quality, especially in mid priced and smaller speakers over the past 20 to 40 years. It is true that speakers and their enclosures don't look much different and the basic mechanics are the same but the sound quality and accuracy has improved significantly for reputable brands.There isn't much innovation in the loudspeaker world
I agree that you don't always get what you pay for. There is a lot of junk out there and some speakers are definitely a better buy for certain uses. OTOH, if you slap some drivers in a drywall enclosure and call then in-wall speakers, you are almost guaranteed to get inferior sound. There is a lot more to speaker enclosure design than building a box between two studs.