If "stability and velocity" are anything but metrics with empirical data as to their validity compared to historical metrics, perhaps you are misinformed about the reasoning behind them.
Adoption of products that enable one particular flavor of org structure that is shown to be useful won't help you if you don't adjust your org structure.
Without adoption of practices that take advantage of those shifts in complexity you will never receive the full benefits from them.
I highly encourage you to research the reasons behind these shifts in complexity, particularly the ways they are intended to increase independence of teams to increase organizational scaling ability.
Empathy is another area to perhaps work on. Because I was that 'single guy' for years and guess what, I missed every family graduation, wedding and funeral for a decade; had months where I had to wake up and restart you jboss instances every 45min 24 hours a day and then still had to be in the office at 9am for meetings where you would punt a ticket to next sprint to fix it.
Platform engineering done right is like an internal SaaS provider, and you should have embeds to help you with interfacing with them. Abstraction to allow for vendor mitigation using tools like Terraform is a good practice but not super custom.
But you can be bitter and complain, working for a company who chooses solutions on the golf course; or you can figure out what your org needs, find sponsors and allies and make positive changes.
If you feel the platform group is adding hurdles, you aren't working at a place that is doing platform engineering or you are understanding why some requirements need to be implemented.
That said as all cloud providers are SoA based, large amounts of custom tooling is a red flag that your org is not SoA based and you are going to have a bad time anyway.
As for manifests and egress, if you didn't care about them before, you probably were releasing insecure, unreliable balls of mud. So yes there will be an adjustment to becoming more of a software engineer. But that is just the reality of working in larger systems on more professional teams.
If you dislike a SoA model, ITIL and ITSM would have been true hell.
The company wide meetings to add basic services were way more subject to bike shedding and blocking in those days.
Anyways being proactive and helping a company alignment with modern practices doesn't happen by itself. If you are passionate about this, run with it.
For some services, copying a jar file is a completely valid pattern in SoA FWIW, and adding complexity without value is an anti-pattern.
Just like with programming, it is easy to forget you aren't the customer and to implement features that your customer don't want or need. Assuming that you don't have a reputation for being a Karen, try communication with the platform team and let them know what your pain points aren't. If they won't let you in the room make your case to someone who will sponsor you to get in the room.
But first realize that having a single person be a single point of failure, then expecting them to sacrifice their entire life to be on call for an entire organization simply isn't realistic.
I wish I hadn't lost two long term relationships and decades of family time doing it. I didn't do me or the companies I was at any favors.