Unfortunately, security updates for iPadOS are inseparably bundled with system software updates; as a result, you cannot have one without the other. If using your iPad online, security updates are arguably critical in maintaining the security of both the device and the personal/sensitive information that is both stored and processed by it.
It is of course your decision to apply updates - or not - and in so doing accept the consequences of either action.
Speaking for myself only, security of the device and my data is the overriding factor in making an update decision; functional and feature changes are a secondary consideration that can, in most cases, be adequately managed via system settings. As with all computing platforms, emerging threats and exploits can only be properly mitigated through patching identified system vulnerabilities. That said, I fully accept that you may have a different priorities and viewpoint.
As to your question as to why the iPadOS 17.7.4 is not available to you, this a question that can only be answered by Apple. Other than the site Moderators, as you are hopefully aware, Apple neither monitor nor participate within these user-to-user forums.
I can however offer the following observations...
1) Following release of a new major version of iOS/iPadOS (usually in September of a calendar year), Apple continue to maintain point-updates for the preceding major version for all compatible devices for a limited period of time. During this period of support, minor feature updates and fixes continue to be released, some of which will be to maintain forward compatibility with the new major version.
2) For devices capable of update to the new major version, point-updates for the prior major version usually cease by the end of the calendar year - at which time the only available updates for these devices are for the new major version. So as to benefit from essential security updates, the only option is to update capable devices to the now-current major version of iOS/iPadOS. It should be noted that, by this time, the new version is very stable and free from any significant issues.
3) For devices incapable of update to the new major version, patches for significant security vulnerabilities are occasionally released for the prior major version - the frequency of these point updates dwindling over time.
Apple invites submission of constructive comments and feedback via is Product Feedback portal. If you have any specific comments or requests concerning future software releases and support, this would be the most appropriate channel through which to direct any such comments. For iPad and iPadOS:
Feedback - iPad - Apple
You should note that while you are unlikely to receive a personal reply, we are assured that all feedback is logged and forwarded to the appropriate department(s) for consideration.