I can see the appeal of that. That is a killer feature for me. My team currently runs what I find to be a pretty lean and clean workflow using Trello, Github (for source control and issues), and Wikimedia for documentation. (Oh, and can't forget Outlook for release scheduling.) Having all of that in one place would make life easier.
On the other hand, not having a monolithic service handling everything has forced us to pay attention to our workflows and practices and keep them sharp.
But the team is small. If we grew or had to manage more projects across multiple teams, this would be really valuable.
I used FogBugz for almost a decade until the most complex projects I was working on dragged me into JIRA. I miss FogBugz' email first interface.
My Current stack is JIRA/Confluence on demand, the integration in the WIKI is simply too good to overlook. For product roadmapping I use Aha.io integrated into JIRA.. it's so far a more capable product than JIRA Portfolio, JIRA portfolio doesn't go high level enough. Harvest in the mix for easy time tracking.
The investment of time in integrating projects between Aha and JIRA so far has been a big payoff. We can literally start noodling with ideas high level, and as soon as those ideas cross the line into an epic, we have the sprint ready to go and automatically created in JIRA.
While it wasn't as smooth, the incredible detail we can manage things that need it, while leaving other simple items to hop through the steps that aren't needed was invaluable.
Most start from scratch projects can be nicely managed in Trello et al.
Generic search alone isn't the feature, or the benefit. None of those options listed have a deep enough search. GitLab and GitHub aren't a project manager - projects that are manageable in Git* likely aren't complex, or enterprise grade.
I have tried nearly every product in this arena as well over 20 yrs of dev in different types and sizes of projects. JIRA begrudgingly is my neccesary evil. I hear nice things about Pivotal Tracker as well, just didn't reach my sphere of folks when I was looking.
Other tools, fogbugz, trello, etc are very good at what they do.
Invariably though when you get enough projects that are complex enough (not always big), JIRA has been the only thing that could take a bite out of managing the details like few others.
JIRA also can be greatly simplified to use but most users don't do this. The JIRA core offering is what I recommend to folks. JIRA is heavier for dealing with heavier projects.
On the flip side. Having a search engine of every issue and decision, be it design, system, implementation, roll out ticket for every project in a company is second to none.
I recently assisted a client in their systems design and growth from from 0 to 50m revenue in 4 years. It feels strange and wondeful to have every decision made in one searchable place, on one time line for every major piece of software or system implemented for them.