Each one fails in its own way. Many servers never send delivery receipts. Read receipts can be declined or ignored. Tracking images are blocked by some programs and loaded in advance by others, such as Apple Mail with Mail Privacy Protection or Gmail’s image proxy.
HawkOpen does not use receipts. It shows the sending state of each message (prepared, accepted by the sending server, bounced), every image load and click with a category, and replies on the Pro and Business plans. Each tracked email tells the recipient that it contains tracking elements.
Where rules that require consent apply, tracking may start only after that consent has been obtained. The link in the message lets the recipient withdraw consent later.