When the movie was made, the graphics were so ahead of their time, they had to hire multiple companies to do the graphics. And they used super computers.
The graphics are mostly important as impressive for the time. The costumes, did not fully work, nor did the sets. But forgive the movie makers that (The visual effect work for the costumes alone, was an amazingly difficult and tedious process, and could be considered a brave experiment.) Instead of focusing on that, I focus on the story. I think of it as a classical "myth" of sorts. You have your archetypes such as Tron as the night, and Dumont as the wise man, etc. It could be viewed in a religious or philosophical vein...there's a higher power of some sort you put your faith in blindly. Or there's technology vs the spiritual aspect of nature, etc. You can see many messages in the story.
Good defeats evil. People's faith is rewarded.
The weakest part is the dialog. Perhaps they simply had too many technical issues to concentrate on better dialog. I think Bridges is entertaining, if nothing else. No one else is really given the dialog to shine, except maybe Dumont and his real world self.
I liked it then when I saw it, and I like it now. But I understand a modern audience may not see what I see.