Simply put he is mediocre overall, despite his body of work being better this season. He has a knack for being beat by edge rushers, and that is where you see the majority of holding calls on him (13 calls the past three years, and leads the line on such holding calls). He has also allowed 13.5 sacks in his career.
He does flash moments of great play, but hasn’t been too consistent in years past. To his credit he has improved in run/pass blocking this season, but has been aided by the re-signed G Ali Marpet who has been outstanding for the Bucs.
The Bleacher Report graded out all starting left tackles in 2017 (must have started 20% of all snaps), and out of 45 LT’s he was ranked 25th. Meaning 66% of the other LT in the league were ranked higher than him. PFF is a little more generous in their grading, ranking him as “above average” or #51 rated tackle. For context, G Ali Marpet was ranked #7.
In today’s league excellent left tackles are hard to come by, and using a high draft pick does not guarantee success (See former Giants LT Ereck Flowers as a perfect example). So that said you could argue that Tampa Bay should make a decent offer because at least you know what you have in Smith. I would argue though, that we could find a better LT through the draft or otherwise in 2019. As you have the opportunity to find great value at a wholesale price. Despite the risk that you might draft a Flowers-esque bust, the Bucs could benefit from a younger/cheaper LT as they try to lock up other key pieces of the team to long term deals.