It wasn't a strong group though. England are good, Croatia decent but clearly in decline, and Czech Republic very much of a similar level to Scotland. I'd argue that Hungary's group was the only strong group in the tournament.
They're not a perfect metric, but Fifa rankings are decent measure of the general strength of a team (3 of 6 groups finished in rank order and the other 3 only saw teams finish above a single higher ranked team), and Scotland's group doesn't appear among the strongest in any measure:
Average Group Ranking:
- Group F (France, Portugal, Germany, Hungary) = 14
- Group A (Italy, Wales, Switzerland, Turkey) = 16.5
- Group E (Spain, Sweden, Poland, Slovakia) = 20.25
- Group D (England, Croatia, Czech Republic, Scotland) = 25.5
- Group B (Belgium, Denmark, Russia, Finland) = 25.75
- Group C (Netherlands, Austria, Ukraine, North Macedonia) = 31.25
Average Group Ranking (Top 3 ranked teams):
- Group F = 6.33
- Group A = 12.33
- Group E = 15
- Group B = 16.33
- Group D = 19.33
- Group C = 21
The group was third weakest in terms of overall ranking, but when you consider that Scotland were the lowest ranked team in it, and therefore had to play three higher ranked teams, their opponents were the 2nd weakest when compared to the teams the other lowest ranked teams had to face.
Additionally, Scotland were the only team lowest ranked in their group to face another team ranked within 10 places:
Ranking Difference (Lowest Ranked to Next Closest)
- Group D = 4
- Group A = 12
- Group E = 15
- Group B = 16
- Group F = 25
- Group C = 38
Czech Republic are simply not a top team, and if anything, one of the weaker sides that qualified (only Scotland, Finland and North Macedonia ranked lower). They've not been ranked higher than 40th by Fifa since the start of 2016, and have been ranked as low as 58th in recent years. Going into this tournament they were ranked 40th, Scotland ranked 44th. Scotland even beat Czech Republic twice in the build up, and have actually beaten them the last three times they've faced each other (going back to 2016).
When you look at Hungary (ranked 37th) having a proper go, leading both Germany (twice) and France in their matches, and Scotland just basically giving it "just happy to be here" and going out with a whimper, it's not hard to see why people might have expected more from Scotland, especially when you consider 3rd place could well have got them through to the knockouts.