depends on how much flexibility and power you want. Are you just working with jpgs, or with raw files as well?
If you just deal with jpgs, I think Irfanview would be great to start out with. It can do raw files as well, but other apps are more flexible, speedy, and powerful for that.
Irfanview is free, and can read pretty much any graphics file (and play some audio files)
I have used it for many years when i just want to resize something (or batches of things), rename files, make downressed email jpgs, look at thumbnails, etc.
I find the sharpening and color management parts less flexible than the Adobe apps I usually use.
https://www.irfanview.com/I think denoising and sharpening take a bit of judgement and learning, in any app.
FastStone Image Viewer is free, for non commercial use, less powerful than the Adobe apps, but probably a bit more powerful than Irfanview
http://www.faststone.org/FSViewerDetail.htm It's pretty easy to use, and you can be familiar with it pretty quickly. It is indeed fast (although a bit slower with raw files than jpgs, at least on my W7 era computer)
I have Lightroom and Photoshop (the last standalone versions of each) and have used versions of both for many years.
they are standards of the industry, but have learning curves. After years using Photoshop, I tried demos of successive Lightroom versions 3 times before i finally sat down and 'did the knowledge'
Once you get comfortable with your most common uses, both are easy. Figuring out how the tools work in any app takes a while, and then becomes a set of habits.
You might consider Photoshop Elements, which is a light version of Photoshop for users who are willing to have the app make a lot of decisions for them.
It's not too expensive (about $100 from Adobe, and often on sale at the usual big photo mailorder/online places (bhphoto, et al)
I have never used it, but i bet it is designed to be easy to use, and does the heavy lifting for folks who don't want to go down the rabbit hole, using a subset of current Photoshop algorithms.
https://www.adobe.com/products/photoshop-elements.htmlA bunch of the newer apps (Affinity et al) use extensive algorithmic file analysis to offer what they think are the most likely useful preset modifications for color, sharpness, etc.
there are lots of online comparisons by various photofora that point out the good and bad points of all of these apps.
tg