XP, in itself, is not bad. But, Win 7 is a "better" OS than XP. Whether Win 10 will be a better OS than Win7 or Win 8/8.1???? time will tell. I don't see a lot of corporate systems being upgraded to Win 10. Many just spent big chunks of $$ converting from XP to Win 7 and new Win 7 compatible applications software and training. The Enterprise versions of Win 7/8/8.1 which are used by many corporate computer systems are not included in the free upgrade.
However, XP is "potentially" less secure and open to malware/spyware, etc, more that newer OS's. The Internet was still growing when XP was released in 2002 and much of the potential malware/viruses were non existent and XP was never designed to combat them. They have upgraded things with Service Packs, security updates, etc but its still not as secure as newer OS'. Microsoft has now discontinued updates for XP. Windows 7 is really to some degree in the same boat. They have discontinued updating the OS. There are still some security updates being issued and Win 7 has until 2020 before its totally stopped being supported at all, just like XP was last year.