I decided to start watching this show in January, and wow, I just didn't like where it went after The Battle for Mewni. I really loved it before this because it was fun, colorful, and hilarious, with all the adventures they went on to numerous areas, coupled in with some really charming characters that showed development, and a decent balance between all of this along with the plot.
Then after The Battle for Mewni, everything became so serious. I wouldn't even mind how serious it got were it not for the fact that it felt so poorly written. What with not-so-great pacing, character development either just not happening or there being complete paradigm shifts that felt forced, and the decisions that were made that never really made sense and their impacts of them being ignored, especially with a lot of people doing bad things and never facing the consequences of their actions.
I don't even want to talk about the romance angle. I honestly don't think that after The Battle for Mewni we went more than two episodes without the next one being focused on various relationships. If it's not that, the episodes then either end up being a ton of exposition or drama. I think the only recent episode that were able to capture the feeling of the earlier ones was Britta's Tacos.
Ultimately, I definitely feel like the show was at its best when it was Star and Marco having fun in Echo Creek for first segment of an episode, then going to some new dimension the second segment. While I am sad that it ended, I think it's probably for the best. The show had over two seasons worth of episodes to get its "seriousness" aspect worked out, only for it to never get any better than when it was first introduced. I'm just upset that they were so dedicated to making the show exclusive that starting with the third season. If they tried to work out a balance between the fun and serious, I would have been fine with that, but it just leaned more so towards the latter than the former, and it never really caught on with me.