It seems to me that it was Lionel Richie who held up Motown toward the end.
The last Lionel Richie album on Motown was
Dancing On The Ceiling in 1986. Between then and the label's official demise in 1989, and excluding greatest hits albums, movie soundtracks, and other compilations these artists had albums on Motown that made the Billboard Top 200 Albums chart:
1986 (post-Richie): Stacy Lattisaw, El DeBarge, General Kane
1987: Bunny DeBarge, Bruce Willis, Smokey Robinson, Temptations, Stevie Wonder
In June of 1988, Motown was sold to MCA and essentially ceased to exist as a separate label, except for compilation releases and reissues of some classic albums from early in the label's history.
I'd therefore be inclined to agree with you, except for one interesting fact: In the 1980s, Richie released all of three albums on Motown. Even though two of the three hit #1 (the first,
Lionel Richie, peaked at #3), there were other artists on the label who had a higher number of charting albums in that decade ... Smokey Robinson, for example, with six.
http://bsnpubs.com/motown/tmg.html