The Scrum Guide sets time-boxes for different sprint events.
Sprint Planning is time-boxed to a maximum of eight hours for a one-month Sprint
While having sprint events that are short might be an indicator of an underlying issue, it can also just be a product of a team naturally evolving it’s process to suit them.
I’ve worked on a few teams that have had short sprint events (planning, retros, and demos). We had one or two half hour backlog grooming meetings during the sprint which would result in a prioritized sprint backlog. Most of planning would be spent deciding how much work the team wanted to commit to and sync up with other teams to review dependencies.
We also had stakeholders who didn’t find any value in seeing demos / sprint reviews. We tried many times to figure out a format that would get them engaged but it never worked, so we ended up scrapping that ceremony all together.
As for retrospectives. They are important but if the team doesn’t want to participate (maybe they are burned out and they just don’t want to do it) then there is nothing stopping you from skipping that as well. I have a few different types of retro formats I follow depending on the teams interest / engagement level. The long version usually follows the format laid out in the Agile Retrospectives book and those can go up to two hours. Shorter versions include the lean coffee format or just simply asking the team for a single idea on a sticky that will help to improve something for the team.
So as long as you are delivering value, the team, POs and stakeholders are happy, and the team is continuously improving I wouldn’t worry about how long your events are.