It's all supply and demand. The expectations from employers as to what a 'qualified' engineer is likely to demonstrate within a 30 min to 1 hour timespan has increased. To get access to the plum jobs you have to be able to pass the gauntlet of interviews and this is something that's not particularly easy if you don't know the 'game'. First thing to realize is that you don't have to be a genius to pass these interviews, however it does require consistent practice and you will have to be dedicated enough to rearrange your life such that you are able to get in some practice on a regular schedule. Of course how feasible this is depends on your life situation. It is easier for younger engineers to dedicate their evenings and weekends to grinding Leetcode than older candidates.
My unsolicited advice is to:
A. Come to terms with the fact that there has been a shift in expectations from employers. Understand that to get the really plum jobs it will require a lot of dedication to get to where you need to be interview performance wise.
B. If you are really rusty, start off with Firecode.io. It provides a more structured approach to studying these interview questions. Once you feel comfortable with the questions there then you can go for Leetcode.
C. Go to interviewing.io and pramp and practice with actual engineers. This will allow you to work on your communication skills. A big part of interviews is just basic communication. You could be rock solid with your algorithms but if you still can't communicate what you are thinking to interviewers in an effective manner you still won't pass the screen.
D. It's not a particularly popular corner of the internet but reddit.com/r/cscareerquestions has a lot of good advice on how you can improve your interview skills. It's also a good place to get a sense of how interviews are structured, how people typically prepare, expectations etc. It's skewed towards getting jobs at the FAANG type of companies but the good advice you will get in the sub is pretty solid and will help regardless of the direction you want to go.
Overall, try not to be too hard on yourself. Technical interviews are an inherently noisy screening tool, and a lot of great engineers fall through the cracks. Preparing for these interviews just like you would prepare for any other important assessment will help you in being more competitive.