Scotland would not be able to enter the EU right away
In the aftermath of the 2016 Brexit referendum, Scotland made its position on the matter clear; 62 percent of Scots favored remaining in the EU.  Since the vote, the Scottish National Party (SNP) has made a return to the EU a major talking point in the independence debate. Unfortunately, there is nearly no guarantee that an independent Scotland would be granted speedy membership or membership at all in the bloc. This may create a dilemma for Scottish leadership, as the EU is quite popular among the country's citizens. In the most recent EU parliamentary election, more than 70 percent of Scots voted for pro-EU candidates. If Scotland is not granted membership in an expedited manner, that may mean several years, or more, of Scotland having to navigate the global stage as a small nation that has historically relied upon support from its more powerful neighbors. There is already a line of several countries that are seeking ascension into the EU, and while Scotland is unique in its being a former EU state by default, it has been given no indication that it can skip the queue. Plus, countries seeking membership must meet economic and political requirements that a newly independent nation may struggle to achieve.  In theory, this may not be of much concern to Scottish nationalists, but it may come at the practical cost of a prosperous Scotland. Without the assistance of the rest of the UK and the EU, Scotland will be green on the diplomatic stage, having to forge fresh agreements and relationships with its European neighbors. Considering the years of debate and discord caused by the UK's departure from the EU, will Scotland want to risk a similar future?
Scotland was once an EU member-state by default, due to its presence in the United Kingdom. This would uniquely place it among the current candidates for membership in the bloc. Not only has Scotland participated in EU parliamentary elections, but it has been a clear supporter of the system. Importantly, former EU Council President Donald Tusk stated that the Union felt "empathy" for Scotland's situation, and would be very supportive of their application for membership. Scotland would still need to go through the necessary motions to apply, but there is clear support for their membership in the EU.
[P1] EU membership is a popular argument for Scottish independence. [P2] There is no guarantee that an independent Scotland will be granted membership in the EU. [P3] Scotland has historically had diplomacy done on its behalf, through its membership in the UK, and as a result the EU. [C] The logistics of becoming a new nation, coupled with the popularity of joining the EU, might be impractical for an independent Scotland to navigate.
Rejecting the premises
[Rejecting P2] Scotland is unique among the nations who would be seeking ascension into the EU, because it was formerly an EU member-state through its presence in the United Kingdom. [Rejecting P3] While foreign policy has not been conducted by Scotland for some time, the Scottish Parliament has been responsible for domestic affairs for more than two decades. They are no stranger to governance.