Morrowind was notorious for bad performance. I know the visuals were impressive back then, but even on a top rig of the time playing at 1024x786 with high/max draw distance was a lag fest in most even on a Geforce 4Ti with a fast Pentium 4. It simply wasn't very well optimised. Leaks everywhere. Not only that, but the game runs so many calculations for almost every action, making it a very CPU intensive game. A K6-III running Morrowind is insane, and nice work for even gettin 10-25fps from that rig!
Also, the only way to get the nice pixel shaded water in Morrowind was to run it with a card that supported Pixel Shader 1.1 (I believe), such as the Radeon 8500 or higher, or the Geforce 3 or higher. Possibly the Geforce 2 Ultra as well. The MX-440's didn't support Pixel Shader 1.1, so you end up with the standard transparent textured water effect but no pixel shaders.
Installing MGE (Morrowind Graphics Extender) allows for some 3rd party optimisations and actually runs the game faster than the original config does at like for like settings. It also allows for modern machines to run at far higher view distances and with more lighting effects.
If I was going to build a rig specifically to get the most out of (unmodded) Morrowind, while keeping it Retro Style (because honestly, Morrowind tends to eat everything you throw at it) I would suggest something like a fast P4 Extreme Edition or simply a 3.4Ghz Prescott, a gig of DDR-400 and a 5950Ultra / 9800Pro. Thats if you want smooth gameplay at 1024x786 or even 1280x1024. I mean just have some fun and build the dream machine you really wanted to own back on the date Morrowind was released! (Only this time will not cost you a silly amount of money) 🤣
I played the shit out of it the week it came out on my crappy Duron 700 with a Geforce4 440MX and it ran like ass. Not much better than your K6-III rig does, if any. Still dumped 400 hours or more into it though. The great thing was I never even finished it that time round. I played it again a few years back on a C2D with a 1950XTX using the Graphics Extender and finally finished it. One of the best games ever made for sure! 😎
I5-2500K @ 4.0Ghz + R9 290 + 8GB DDR3 1333 :: I3-540 @ 4.2 GHZ + 6870 4GB DDR3 2000 :: E6300 @ 2.7 GHZ + 1950XTX 2GB DDR2 800 :: A64 3700 + 1950PRO AGP 2GB DDR400 :: K63+ @ 550MHZ + V2 SLI 256 PC133:: P200 + MYSTIQUE / 3Dfx 128 PC66