With the state of software development today, I'd be more worried about how many other holes they've added in the process of fixing something or introducing unwanted new "features"[1].
Here's some interesting statistics to look at and compare...
https://www.cvedetails.com/product/462/Microsoft-Windows-98s... - 30 RCEs in 7 years
https://www.cvedetails.com/product/739/Microsoft-Windows-Xp.... - 276 RCEs in 20 years
https://www.cvedetails.com/product/32238/Microsoft-Windows-1... - 664 RCEs in 8 years
https://www.cvedetails.com/product/102217/Microsoft-Windows-... - 157 RCEs in 2 years
More relevantly:
https://www.cvedetails.com/version-list/1224/19997/1/Google-...
However that ignores the fact that publicly known exploits are more dangerous for the average user than zerodays.
Well, I'm not. If he wants to daily drive Windows 98 because it had fewer documented RCE vulns, godspeed to him---and he probably will be more secure, just by virtue of good ol' security through obscurity---but that is not a reasonable solution for 99.999howevermanyninesyouwant% of computer users today.
The rate of finding exploits and what the definition of a vulnerability is really what has changed - now the definition of is much broader while at the same time, exploitability has dropped off due to mitigation in modern operating systems, compilers and CPUs. Overall, we get far more exploits, but far less of significance.