I visited Mexico between February and April 2019. I visited most WH colonial towns around Mexico City and Morelia was the first one.
The historical center of Morelia is not a breathtaking place, but the city is beautiful and the feeling walking around was really enjoyable. With its pink stone facades, la Avenida Madero and la Plaza de Armas, the city looks unique among Mexican towns. The focal point of any visit to Morelia is without a doubt the cathedral. It is impressive, massive and harmoniously mixes many architectural styles. Make sure to look at the 4,600 pipes organ inside! The cathedral is also nicely illuminated at night.
Among other sites I've visited, it is worth mentioning el Santuario de Guadalupe. This spectacular baroque church is heavily decorated with golden and colored ornaments. It is located on the beautiful Plaza Morelos, from which you can take la Calzada Fray Antonio de San Miguel, a nice pedestrian street that leads to la Fuente Las Tarascas. El Acueducto, even being less impressive than Querétaro's one, is still beautiful and nice to walk along. La Plaza San Agustin, el Jardin de las Rosas, el Bosque Cuauhtémoc, la Biblioteca Publica de la Universidad Michoacana, and la Plaza de San Francisco are other nice sights.
Logistically, Morelia is a big city with plenty of transportation options. I reached it from Angangueo (Monarch butterfly sanctuaries) via Zitacuaro. There are also many buses from Mexico City. I then traveled west to Uruapan (no WHS heres, but you should check out Paricutin Volcano!) and then to Guadalajara. It is also possible to travel to Patzcuaro, Colima or directly to Guadalajara. Within Morelia, combis go everywhere for really cheap and you never need to wait for long. Morelia is a university town with lots of students around. The atmosphere is thus nice, there's a lot of bars and restaurants and they are cheap. Make sure to taste dulces morelianos while you are here. These candies are famous in the region and really good!