I'm cross posting this from the premium slack because it was raised that the answers might help the broader community.
I work for a small company - the engineering org is approximately 60-70 people all told. The company is about a decade old, but has grown more recently, and I joined the small SRE/Developer Tooling team within the last year. Historically, the company has operated at a relatively slow pace, and followed practices that are, politely, out of date. Just to give an example of the kind approach the company takes:
In my role, I've been pushing for change where possible, trying to evangelize the better ways of working, such as Infrastructure as Code, logs sent to a centralized location like Splunk, and deploying to other AWS regions to assist in both regional lag and general DR/failover concerns.
Thankfully, there's definitely some purchase there by leadership, at least on a high level, as they're generally receptive to these changes and recognize that they cannot continue with the same old practices. However, this mentality doesn't appear to be flowing through to the rest of the engineering organisation. My team and I are repeatedly asked to revert changes we've made, often because developers are merely used to the way things used to be, or because PMs/teams want to stick to a schedule or speed that was only possible via shortcuts (such as manually provisioned infrastructure). All of this has happened despite repeated public comments by some in leadership against those requests specifically.
What can I do to push for these kinds of changes, when I'm not in any kind of official management or leadership position? I have no official power beyond a general remit by my manager to uphold certain standards for my team.
At my previous startup, I was in the same boat. I was constantly trying to learn and apply best practices because the codebase I was working on wasn't great and the engineers took a slower, more relaxed approach to development. Ultimately, close to zero attempts to change the culture happened and I ended up leaving for greener pastures. While my scenario might not exactly be the same as yours, hopefully bringing in some of that perspective will help paint a clearer path forward.
How I (as a tenured senior engineer) would approach a world where things aren't great is to identify the problem as 1 simple truth. When problems are identified as a single, simple truth, it's much easier to understand them and to align on them (less is more). If you provide a list, you will overhelm others. If you jump directly to executing this list of things, you're perceived as engineering for the sake for engineering (which reduces your social capital). From your description of the response to your changes, it's clear to me that you started with the list and not a simple truth. Develop the 1-liner statement first and get alignment on that statement. When asked to clarify, state both your perceived observations and the impact together. Bucket things into higher-level problem groups: again, simple truths are much easier to be understood compared to "here's a list of everything to fix". In your situation, you can try something like "Our legacy tooling and practices is slowing development down. I have observed x, y, z themes of scenarios in which this is visible".
Once you've aligned on the simple truth, then identify what is the single, most impactful effort you can do to mitigate the problem. This will narrow down the surface area of your changes, lowering the changes you need to make and how many new things other engineers need to learn. You also want to treat each effort as a risk. Every effort you attempt can fail by making it appear you made the status quo worse. If you reach a point where you've made multiple changes and ended with more unsuccessful changes than successful changes (your value is negative from making things worse more than better), you'll have no social capital and will likely get PIP'd/fired soon. Comitting to one thing also establishes focus: you won't need mental overhead to juggle competing priorities.
Once you're identified what effort to focus on, you need to minimize the blast radius of developers impacted by your efforts.
Once that individual is clearly sold on your changes, look to onboard their team. Work with this individual to help sell the team on the benefits of your changes and help onboard the team to them. As a member of the team, their team will trust what they say (and that includes their vouch for you). After some reasonable amount of time (up to your discresion, have them fill a simple survey with a single yes/no question: are these changes an improvement to your current workflow? If less than 67% of respondents say "yes", iterate on the feedback of people who said "no" until you have at least that 67% ratio.
After that, it should be a relative breeze: onboard more and more teams onto your chages and keep surveying them to make sure you maintain at least a 67% ratio for people who are happy with your changes. Once the majority of folks who benefit from the change on onboarded, work with management to put a date to delete the old stuff and to move everyone onto the new changes. At this stage, there will be little to no questions: there's clear metrics around the benefits your changes and there's people who will vouch for you. The worst scenario for people now is that they are bregrudgingly willing to migrate.
Finally, you're done! Now if people want you to keep going, pick the next most impactful change and repeat the process starting at working with 1 person.
To compress this down to make it easier to extract learnings: you are probably in the right for taking on efforts to improve tooling and infrastructure, but your gaps are around understanding the people around you and your standing with them. Given their responses to your effort, you tried to directly replace existing tools/processes without direct and thorough consulation with ICs to build clarity, empathy, and trust in your efforts. For me, your current approach would only work if you were a tenured staff+ FAANG engineer in a company with 0 ex-FAANGs (then it's inefficient for everyone/anyone to fight your efforts compared to unceremoniously complying). The key lesson is that social capital impacts your ability to execute: if your name or resume doesn't immediately demand respect, then you need to build up social capital. The larger the blast radius, the more social capital you need. To avoid efforts with larger social capital needs (like company-scoped infra migrations), break down the effort into an incremental set of small steps. The process will be slow, but that reflects on how we (as humans) are generally slow to change.