I think that's fair. When we started back in 2016 with Lambda, it was similar to how you describe it.
Now we've got a ton of companies that just use Lambda. So you can imagine a team for 50 developers, working on 40 or so separate services, with 500 or so Lambda functions. It can be hard manage the tooling for all of this internally.
When you are at a team of 50 working on 40 separate services with 500 Lambda's or so I don't see how you are better off than writing a self contained service that's deployed as a single artifact i.e microservice.
You get the advantage of all related code grouped together, easy to instrument / test / run on any platform. All the advantages of a mono repo but at a service level, non of the orchestration or special tools to deal with 500 disparate lambdas and wiring up event sources / sinks.
I think the complexity aspect is a fair criticism of Lambda.
The way I look at it is that, as a developer, I want all the advantages of serverless (per ms billing, scaling up instantly, scaling down to 0, etc) while not having to worry about the function level nuances of tooling and deploying.
Having struggled with scaling large systems in a past life, I personally lean more towards taking on the burden of tooling instead.
To expand on that, you can build this tooling out internally and many teams do. They just have a team dedicated to building and maintaining something like Seed internally.
What we bring to the table (aside from being more cost effective than staffing for this), is that when we solve an issue for one of our users, it gets solved for everybody else that's using Seed.
In fact, that's how we solved some of the issues around "reliably deploying a large number of serverless services together". One of our users was running up against some errors related to this and we worked with them to figure out the issue and fix it for everybody on Seed.
Now we've got a ton of companies that just use Lambda. So you can imagine a team for 50 developers, working on 40 or so separate services, with 500 or so Lambda functions. It can be hard manage the tooling for all of this internally.