Shared hosting gets blamed for everything and about half of that is fair. What finally moved me was noise, not raw speed: one neighbour on the box would run somethign overnight and ttfb on all 5 sites went from 380ms to 4 secodns until the host restarted php. Support kept telling me to install a caching plugin. Caching does not help a first byte that is stuck in a queue behind someone else. The whole idea of hosting shared between a few hundred accounts is that you get the average, never the peak.
The move itself was boring. Ttl down to 300 a day ahead, files and db copied to the new host, a hosts file entry pointed at the new ip so I could test every site properly before anyone else saw it, then dns flipped during the client's dead hour. No downtme, and the old box stayed up for three days after in case. Shared hosting is fine for a brochure site nobody touches. It stops being fine the moment the client's billing depends on the page loading.
Source: r/SiteManagement · by /u/emilmarek