"MUCH more" is an overstatement without going back to 3.5 style tactical grid movement & AoOs Delivering a touch spell was risky back then because moving more than 5 feet could provoke an AoO & being that close meant you were probably close enough to be a viable target. At best a bonus action touch spell is very very slightly more difficult with how 5e currently handles the tactical grid elements.
It is much more difficult. For one thing you have to have enough movement and a path to the person you are trying to heal and at least half the time you don't have that.
Remember moving through friendly creatures space is difficult terrain as is .... well difficult terrain .... and you can't move through enemies at all unless they are two sizes different (and again it is difficult terrain). IME about half the time you will not be able to get in touch range at all on your turn in the middle of combat and when you can it will often be extremely dangerous and tactically unsound.
This is before you consider a number of conditions, most notably frightened and grappled, that will prevent you from doing it.
IF you are relying on touch spells in combat you really need a flying familiar to deliver it effectively and reliably.
With healing word you bypass all of this.