I've used them quite a lot around Europe and once or twice in Africa (and even locally, when I didn't have an unlimited data plan and used all of my allotted data by my carrier and it was easier to just buy an eSIM), and my experience has always been pretty good.
Note that I am talking about these Airalo, Nomad, etc eSIMs sold online, not eSIMs sold directly by the carrier themselves (the latter would generally be as good as the carrier's own prepaid offering).
>I've tried a few of these and can rarely pull more than a few megabits per second (in a location where a carrier's own SIM pulls 150+).
That seems.. fine? If you're traveling and your use case is checking google maps, or logging into airbnb to pull up your booking, you don't need 150 Mb/s of speed and low latency. The only case where it might be dodgy is if you're doing voip calls or watching streaming videos, but why are you doing those things on vacation? Sure, it'd be nice to have a local sim with low latency and high speeds, that's often much more expensive than esims and/or comes with more hassle (eg. KYC or having to pick up the sim in-person).
It depends if they're building new towers or just upgrading existing ones. Doing a like-for-like swap can presumably be done entirely by the vendor, setting up new sites indeed needs a bit of work, so maybe whatever little technical staff they have handles that (or maybe even that is outsourced too).
> How about MVNOs and eSIMs?
When it comes to MVNOs it depends whether the MVNO runs (at least parts of) their own infrastructure or is just white-labelling the upstream carrier's one.
In the former case they can indeed do it, but the company culture challenges still apply. You need to hire and retain good engineers, something I'm not aware of any telecom company actually prioritizing. Meaning they too will eventually end up with a ball of mud in a few years.
In the latter case they're just reselling the upstream turd with a bit of polish. If the upstream ball of mud can't manage eSIMs, they can't either.
> I've only done the travel eSIM thing
I wouldn't recommend relying on these. You're getting bottom-of-the-barrel capacity that (even if it works) is so slow that you'd be lucky to even use up half your data cap. You are always roaming and your data is tunnelled through what feels like some dial-up modem in some shady warehouse. These are a scam.