That speed thing will be fine, which is much worse, if your flash memory gets corrupted or your phone won’t boot at all due to chip or motherboard issues, so you can’t manage your memory anymore (encrypted). So you have lost thousands if not tens of thousands of photos and videos.
Since your processor and/or your other components are currently locked to each other via an external security processor, you can’t do much except sync to the cloud (not secure).
I know quite a few people where their phone no longer starts and they lost everything. Because people just never thought that an SD card could be used or didn’t know.
Samsung did it with the S6, removing the microSD card slot and after much criticism of the S7, they quickly went back to it.
https://www.androidplanet.nl/nieuws/galaxy-s6-micro-sd/
https://www.rtlnieuws.nl/…alaxy-s7-net-niet-perfect
In addition, there are already many reliable cards on sale with decent speed and a good controller. Samsung can’t stop people from inserting el cheapo cards, but they always warn about the memory leak.
I think the real reason behind the omission of the microSD slot is that it provides yet another entry point for security vulnerabilities. Bit of the Rubber Ducky or BadUSB as a principle. It’s not for nothing that Samsung has KnoX to mitigate things like that.
