I agree. Uploading content that is not yours actually goes against itch.io's terms of service
Publishers are solely responsible for the content they upload and distribute on itch.io. Publishers affirm, represent, and warrant that they own or have the rights, licenses, permissions and consents necessary to publish, duplicate, and distribute the submitted content.
The Company does not endorse copyright infringing activities or other intellectual property infringing activities and violations of may result in the removal of content if the Company is notified of such violations. Removal and termination of accounts may occur without prior notice.
Abandonware websites are well aware of the risks of using abandonware. For example the website My Abandonware both encourages users to purchase software legally (if it is available) and shifts all liability onto users for using their site.
We allow you to download old games for free, but we do not take any responsibility for downloads considered illegal in your country. Please try to buy the game first: GOG.com, Steam, Amazon or eBay may be selling your game.
I should note that a lot of software that is considered "abandoned" is relatively old and the proper owners may be difficult to identify or contact. This is not necessarily the case on itch.io where many users who delete their content may continue to be active on the site.