Yes it could be a lot of things. I really try to find the solution to make the subtitles look HD but something is wrong and I don't know why. Maybe the problem is my monitor or my gpu but I can't change them so... Still looking to find out what the problem may be.it's operator error aka your inexperience
watch bunch of youtube tutorials and read blog posts
youll eventually figure it out
could be something just wrong with your screen resolution. could be you are using incorrect settings on export. could be hardware limitations like you said. could be 100 things. thats the beauty of troubleshooting. lots of homework ahead of u.
shortcut to your solution may be...download some premium template for w/e software you are using that has HD subtitles on it. then reverse engineer it (to see how it differs from how you were doing it wrong).

