That's what Java applets and plugins were for.
I'm also pretty sure they weren't the first to fetch data from the server without reloading, because people were doing all sorts of novel things in the mid-90s with plugins.
The reason it didn't really take off back then wasn't because of vision. It was because there was so little you could do with JavaScript. The browsers were still implementing the basic features and a lot of page/component manipulation was very broken. Applets and plug-ins were so much more capable.
Then along came Javascript with its transparent attempt to ride the coattails of Java by adopting a similar name. No interest in that either.
Also, Java applets and JavaScript were added to Netscape 2.0 at the same time and were meant to complement each other, not compete. It may seem like Java came first because JavaScript was called LiveScript for the first three months. I also don't think the JavaScript name change was intended to ride the coattails of Java, rather it was clarify and harmonize its relationship to Java.
I still look back and I'm amazed at how much stuff happened between the summer of '95 and winter '96. Windows 95 release. Netscape went public. 2.0 released 1 month later introducing Java and JavaScript, etc. etc. etc.
I think the point I'm really trying to make is that the Netscape team had a much richer vision of the web than what we use today. Before they built Netscape, Andreessen and Clark were considering building an online gaming platform. I'm sure you remember how big multimedia was back then.
If you look at the timeline, you can see where the were going. They started off with a focus on dominating the browser market, which they did in 4 months. In less than a year after their first release, they released the first version of an online platform. It added Java, JavaScript, and a plug-in architecture with standard plug-ins like Live3D so you could embed VRML into your HTML page. No one was even sure HTML wasn't going to be replaced by something better, so I have to imagine they were hedging their bets by adding three different ways to build on their platform.
If anything, I think your original comment reinforces that strategy. They knew there were a lot of C++ developers who wouldn't take to Java for whatever reason, so they offered a plug-in architecture for people who cared more about performance and experience than being cross-platform.
Had things gone differently (Microsoft not woken up), I can easily see Netscape creating a dominant internet platform that went beyond HTTP and viewing hyperlinked documents. They were already bundling email, website editors, conferencing, news clients, etc.
And they are still doing it. CSS Grid is not even 3 years old.
Except that they couldn’t alter the DOM, or handle events on DOM elements, the two things that developers really needed (even if they didn’t know it).
When DHTML was introduced in '97-'98, the only major browser that had a reliable DOM was IE until Firefox came around in 2002. Netscape tried, but it was buggy to the point where there were no real workarounds to the huge gaps in missing functionality.
As far as 1995 was concerned, applets and plugins looked like the future. Honestly, the web was so new and so inferior to other things in 1995 (Macromedia, WYSIWYG tools, etc.), I think most of us saw HTML being replaced in a few years by a richer clients, applets or plugins.
Plugins and applets filled a huge gap functionality wise.
I don't say that to crap on Netscape. Microsoft was a well-funded company with a lot of experts who had years of experience create applications with DOMs. Also, they had the luxury of delivering a browser for one operation system.
Netscape was a brand new company that went public 7 months after it's first release and 1.5 years after its founding. They sold investors the premise they were going to become the Microsoft of the internet. They had a fraction of the resources while they were trying to creating browsers, email clients, collaboration software, web server, and a host of other software for multiple platforms.