Alriiiiiighty, look what my idea was. This is what I had planned for a theme, give it a classic rpg game vibe:
https://strategy.thardferr.com/tech-tree-prototype.html
Researched techs appear brighter, maybe put a glowing light behind them for extra emphasis (this thing only took me like 1 hour to mockup, so it def needs some polishing). Click to open a box with more info and research button.
I like it because it makes seeing what you did easier, and looking forward to see what's next. The visual element gives more immersion, slightly more modern than the old one, maybe just enough.