You may well laugh at WinME, it more than earned everyone's derision.
But Win98 SE (Second Edition) was actually a very good single-user, personal (non-business), non-internet OS. It had no security to speak of, but then, those were arguably more innocent days. :-)
I have a VM (virtual machine) of Win98SE. On modern hardware it screams, and it runs my few remaining ancient 90's applications, frankly just as well as Win7 does.
But rather than upgrade to WinME, I would either stay with Win98SE or migrate to WinXP. Granted, Win2000 defined my ideal desktop GUI, and forever afterward, my first steps when installing a fresh copy of XP or 7 is to set the desktop GUI back to Win2000 mode. The fact that Win10 blocks me from doing so (even with the addition of ClassicShell) is one of the reasons I refuse to run Win10 as my default Windows environment. I have a Win10 VM around for software compatibility testing, and to run a few Win10-only applications, but no more than that.
So I'd say, stick with Win98SE if that's what you like. Why? Because it's NOT vulnerable to this attack!! LOL, seriously; AFAIK this vulnerability like most other ones these days, only affects the NT-based editions.
OTOH, stay the heck off the internet with Win98 or any of the DOS-based Windows. They're totally vulnerable to a million other attacks.
Sorry for not seeing this reply till now, but in conjunction with what you said, I noticed long ago when switching to XP on much better hardware that on basic tasks, like opening folders or something like Notepad, that W/9x was noticeably faster. Things would just like instantly jump into view, whereas with XP and later there was a bit of a lag. Although on this AMD 4350 (4.2ghz) basic things come up very quickly unless the CPU is heavily laden (and under 9x that meant keeping an eye on system resources). Thank God for what we have under grace in Christ.