" I would not dare to disagree with Masq,"
LOL - this is hardly heresy :)
If the dust is that bad it's certainly easier to remove carefully by hand. My experience with compressed air without opening the case is similar to yours which is why I only recommend clearing it with the case open so you can directly see what's happening.
>> laptop fans are just not built at the standards that they should be << yep they save every penny they can, and make sure the lifetime does not exceed 3*4 years average
Check heatsinks and thermal pads/paste are connected.
Reassemble and test again
https://www.myfixguide.com/lenovo-thinkpad-x270-disassembly-ram-ssd-hdd-upgrade-options/