#2 The title has lost significance

Lesnar being Champion means we rarely see the title on Raw and therefore it has lost some significance. The Universal Title is meant to represent the holy grail, the belt that Superstars are vying for, each week on Raw. There was a time when the belt would be defended on Raw, but with Lesnar only wrestling on pay-per-views, we don't get this.
The WWE Championship, currently held by AJ Styles, has much more significance than Lesnar's title because it features weekly on SmackDown Live and since Lesnar is a part-timer, so is his title.
Details of Goldberg's last match HERE
Having a full time star hold the belt and show up with it each week on Raw puts the spotlight on it more, and therefore makes it more significant.