Exactly! I have the same experience. It is a source of eternal frustration in the team. I had situations that everyone was crushing it, the team work efficiently and at the end the team had to go through the bashing on retro.
There is an argument that you can always add features to the sprint, so you start small and then extend sprint with additional task. But it does not work, because tasks seem to take all the time that was planned for them.
However, the rituals of SCRUM like retros and groomings taking place every 2-3 weeks is a good thing. It's like hygiene.
That's very good and any ISO 270001 certified small-medium company would need that. But it would be better to have stand alone web interface and not only relay on Slack.
If you are far behind start with Khan Academy. Then there are MOOCs on Coursera and eDX as well. Less interactive but 100% Real deal (and it doesnt mean harder) are course materials often with videos from MIT Open CourseWare. If you are into ML do Gilbert Strang Linear Algebra. It will develop you so much that it can’t be understated. Buy his book and do exams and assignments. If you want to take pleasure in math there are brilliant channels on yt, for example Numberphile. GL man.